- Email: [email protected]
Validation of the Seasonal Pattern Assessment Questionnaire (SPAQ)
JOURNAL OF
Al#EC’FI
ELSEVIER
DISORDERS
Journal of Affective Disorders 40 (1996) 12 I - I29
Validation of the Seasonal Pattern Assessment Questionnaire ( SPAQ) Andres Magnusson Department of Psychiatry, Received 6 December
Ullrobl
Hospital, 0407 Oslo, Norway
1995; revised 28 March 1996; accepted 28 March 1996
Abstract The validity of the Seasonal Pattern Assessment Questionnaire (SPAQ) was examined by interviewing 81 individuals who had participated in an earlier community survey of seasonal affective disorder (SAD) in Iceland. When SAD and subsyndromal SAD (S-SAD) were combined into a ‘winter problem’ group, the questionnaire’s sensitivity, specificity and positive predictive value for that group were 94%, 73% and 45%, respectively. The SPAQ discriminated poorly between SAD and S-SAD, and hence it had a poor case-finding ability for SAD. Clinical evaluation verified a diagnosis of SAD in individuals who had no previous information about this syndrome. The questionnaire furthermore identified a group of individuals who had generalized anxiety and marked seasonal variations. Clinical evaluation arrived at a similar prevalence rate of SAD as the questionnaire. Keywords: Seasonal affective disorder
; Seasonal Pattern Assessment Questionnaire;
1. Introduction Seasonal Affective Disorder (SAD) is a condition of regularly occurring depression during autumn or winter with remission the following spring or summer (Rosenthal et al., 1984). This disorder causes significant distress, but an effective treatment is available (Terman et al., 1989). A milder form of SAD, termed Subsyndromal Seasonal Affective Disorder (S-SAD), has also been characterized (Kasper et al., 1989b). It is important to have valid instruments to identify the individuals who are likely to suffer from SAD and S-SAD and to be able to estimate the prevalence of these disorders in the 0165-0327/96/$15.00 Copyright PI/ SO165-0327(96)00036-5
Sensitivity;
Specificity;
Anxiety disorder
general population. The Seasonal Pattern Assessment Questionnaire (SPAQ), developed by Rosenthal et al. (1987), is a widely used instrument to screen for SAD. A central feature of the SPAQ is the Seasonality Score index. This index has a good test-retest reliability (Hardin et al., 1991; Thompson et al., 1988). Thompson et al. (1988) and Kasper et al. (1989b) have found that groups of subjects with SAD, S-SAD, major depression without a seasonal pattern, and normal individuals, had significantly different mean scores on the Seasonality Score Index. The Seasonality Score Index has been reported to correlate well with Hamilton Depression Rating Scale scores (Kasper et al., 1989b).
0 1996 Elsevier Science B.V. All rights reserved.
122
A. Magnusson
/ Journal
of Affectire
The SPAQ was originally designed and used as a first line screening instrument, and the index cases were subsequently interviewed and diagnosed clinically. However, in recent years the use of the SPAQ has been extended. Criteria have been developed to identify subjects who are likely to have SAD or S-SAD (Booker and Hellekson, 1992; Kasper et al., 1989a; Magnusson and Axelsson, 1993; Rosen et al., 1990), and the questionnaire has been applied in epidemiological studies of these disorders. Several have already been published (Booker and Hellekson, 1992; Ito et al., 1992; Kasper et al., 1989a; Magnusson and Axelsson, 1993; Magnusson and Stefansson, 1993; Mersch et al., 1995; Rosen et al., 19901, and the questionnaire is presently being used in hitherto unpublished epidemiological studies in Finland, Canada and Norway. This use of the questionnaire requires more stringent validation procedures than have previously been undertaken. We are not aware of any studies that have examined how well the SPAQ estimates prevalences of SAD and S-SAD, and the SPAQ’s sensitivity, specificity and predictive value are, to our knowledge, unknown. The aim of this study was to validate SPAQ classifications of SAD and S-SAD against clinical diagnoses and to examine the SPAQ’s ability to estimate the prevalence of SAD and S-SAD.
2. Methods 2. I. The questionnaire The Seasonal Pattern Assessment Questionnaire (SPAQ) is an instrument for investigating mood and behavioural changes with the seasons. It has several scales. One of these, the Seasonality Score Index (SSI), has six items that measure seasonal variations in mood, appetite, weight, sleep, energy and socialising. The sum of these items is the Seasonality Score (SS), which can range from 0 to 24. Other scales evaluate, for example, the degree to which the seasonal changes are experienced as a problem and in which month of the year the subjects feel best or worst. These three scales are used to classify whether the respondents have SAD, S-SAD or neither of these disorders. The questionnaire was provided by Dr. Norman E. Rosenthal at the National Institute of
Disorders
40 (19961 121-129
Mental Health, USA. It was translated to Icelandic and then back-translated to English to verify accuracy of translation. 2.2. The subjects All 81 clinically evaluated subjects in this study were selected from respondents participating in an earlier community epidemiological study of SAD in Iceland. Iceland is a Nordic country with high educational standards. The procedures of the epidemiological study have been described in detail elsewhere (Magnusson and Stefansson, 1993). Briefly, the SPAQ was mailed to 1000 individuals, randomly selected from the Icelandic National Register in spring 1988. The response rate was 61%. The SPAQ case finding criteria for SAD in the epidemiological study were: An SS of 11 or higher, and experiencing seasonal change as a problem at least to a moderate degree. Furthermore, the subject had to feel worst during one of the winter months. The SPAQ criteria for S-SAD were those of Kasper et al. (1989a): (1) feeling worst in the winter months; (2) a SS of 11 or more; and (3) experiencing seasonal change as a mild problem or no problem at all. Those who had a SS of 9 or 10 and experienced seasonal changes as a problem, at least to a mild degree, were also classified as having S-SAD. These criteria classified 19 individuals as having SAD and 38 individuals with S-SAD in the epidemiological study. In the present study, all those 19 individuals, classified to have SAD in the epidemiological study, were clinically evaluated. Twenty randomly selected individuals from those classified to have S-SAD in the epidemiological study, were also evaluated. Furthermore, two control groups were made up from the respondents of the epidemiological study. One was a contrast group with 21 individuals who reported that their mood and behaviour were virtually unaffected by the seasons. They scored 0 or 1 on the SSI (referred to below as ‘the non-seasonals’). The second control group consisted of 21 individuals who were randomly selected from all the respondents who had not received SPAQ diagnosis of SAD or S-SAD. This latter control group was used in calculations of sensitivity, specificity, predictive value and diagnostic reliability. In the epidemiological study, no cases of Summer SAD were found, hence SAD
A. Magnusson/ Journal ofAffectil,e Disorders 40 (1996) 121-129
refers in this paper to winter SAD. The SAD S-SAD groups combined will be referred to as ‘winter problem group’. After the procedures been fully explained, all participants provided formed consent.
and the had in-
2.3. Ecaluation All 19 subjects who the SPAQ classified as having SAD in the epidemiological study described above, were contacted. They were all willing to participate in the present study. Only one of these dropped out, but a diagnosis of SAD or S-SAD had by then been excluded. Four individuals had been admitted to psychiatric wards. With their consent, information was gathered from hospital records and the diagnostic criteria discussed with their psychiatrists who had followed them over time. These diagnoses were considered superior to a manual diagnosis and they were not further diagnosed. Of the remaining 14 subjects, 11 completed a full Diagnostic Interview Schedule (DIS) interview, administered by a trained person not otherwise involved in the project. The remaining three individuals did not wish to participate in a full DIS evaluation, but were evaluated by a clinical interview, and by SIGH-SAD ratings (described below) in winter. When interviewing those who did not complete the DIS interview, the main focus was on SAD and mood disorders, and no attempt was made to screen for all the diagnoses covered by the DIS. In addition, all 19 subjects were interviewed by the author, and 15 of them were rated by a blind rater on the SIGH-SAD in winter. If the subjects had previously contacted psychiatrists or general practitioners for psychiatric problems, information was collected from these sources with the patients’ consent. The S-SAD group, the non-seasonal group, and the randomly chosen control group, were evaluated for symptoms of SAD by a clinical interview. The mood disorder part of the DIS was administered to obtain an objective diagnosis of SAD. A blind rater attempted to rate the participants in winter on the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version (SIGH-SAD). This is a structured interview guide which incorporates the Hamilton Depression Rating Scale and 8 additional items
123
that evaluate the atypical depressive symptoms of SAD (Williams et al., 1988). The SAD group and the non-seasonals were contacted between 15th December 1990 and 15th February 1991. Most of the SAD subjects felt that they were within their difficult winter period at the time of rating. The S-SAD group was reached between 15th February and 15th March. By that time, all but four of the subjects felt that their winter symptoms were already starting to wane or had disappeared. The reference standard was the application of the DSM-III-R criteria for SAD (American Psychiatric Association, 19871, using all available information, and adhering to the DIS or hospital chart diagnosis of a major depressive episode. S-SAD has been defined by Kasper et al. (1988, 1989b). In the present study, the reference standard for S-SAD was a clinical application of Kaspefs criteria, slightly modified as discussed below. To assess diagnostic reliability, a psychiatrist not otherwise involved in this project evaluated blindly the data from 24 subjects, 8 of whom the SPAQ had classified as SAD, 8 as S-SAD and 8 subjects chosen randomly from the individuals classified neither to have SAD or S-SAD. The kappa value for these 3 diagnostic groups was 0.8 I. 2.4. Statistics Sensitivity, specificity, positive predictive value and weighted kappa were calculated as described in Altman’s Practical Statistics for Medical Research (Altman, 199 1). The non-seasonal group was excluded from these analyses, since their inclusion would have given an artificially high specificity and positive predictive value. Confidence interval (exact test) was calculated by the Confidence Interval Analysis computer program (Gardner et al., 1989). Power for statistical tests was calculated by the Epi info version 5.1 computer program (Dean et al., 1990)
3. Results 3. I. Validation of SPAQ classifications When the subjects classified as having SAD or S-SAD by the SPAQ were interviewed, all except
A. Magnusson/Joumal
124 Table 1 Winter symptoms
of Affective Disorders 40 (1996) 121-129
in relation to SPAQ classifications. SPAQ classifications SAD
n
Sex M/F Mean age (years) Symptoms in the winter: Depressed mood, dysphory Lack of energy Mean increase in sleep duration, min (SD) Mean increase in body weight, kg (SD) Mean SIGH-SAD scores in winter ’ (SD) Psychosocial stress more: in winter(W) in summer(S) Winter symptoms occur regularly The symptoms lift in the summer A major depressive episode Results from the seasons. a No specific b Individuals ’ II = 15 for
S-SAD
Non-seasonals
20 6/14 34.5
21 13/8 41.1
83% 89% 123 (971 1.6 (2.6) 17.3 (11.2) W=l
75% 55% 59 (611 1.7 (2.1) 4.0 (3.1) w=2 s=2
_a _a
100% 84% 8
95% 85% 8
19 10/9 33.8
clinical interviews with subjects who the SPAQ had classified
b
1.2 (17) 0 1.8 (3.4) w=4 s=5 0% _a 3
into 3 groups: SAD, S-SAD and subjects virtually unaffected
by
winter symptoms. in this group had a Seasonality score of 0 or 1. SAD, 18 for S-SAD and 21 for non-seasonals.
one said that their winter symptoms recurred regularly. Most of these subjects also felt that their symptoms remitted fully in the summer (Table 1). The mean SIGH-SAD score in the S-SAD group was significantly different from both the SAD group (t-test, t = 4.46, P < 0.001) and the non-seasonals (t-test, t = 2.12, P < 0.05). No individuals were found whose symptoms of SAD or S-SAD could be accounted for by seasonal variation in psychosocial stress or anniversary reaction. A major depressive episode is considered a prerequisite for a diagnosis of SAD. Of the 81 individuals studied, 19 had experienced a major depressive episode. Three of these belonged to the non-seasonals and their depression had no relation to seasons. In the winter problem group, there were 5 subjects who could not be given a clinical diagnosis of SAD although they had experienced a major depressive episode. These were the individuals who generally had the most severe depression in the sample. Although they felt that their symptoms did improve substantially or disappear during the summer, records from hospitals and private psychiatrists
could not confirm this, The remaining 11 subjects with major depressive episodes were given a clinical diagnosis of SAD. Only two individuals, whom the SPAQ had classified as having winter problems, had upon clinical evaluation too mild symptoms to warrant a diagnosis of SAD or S-SAD. In the randomly chosen control group, two subjects were diagnosed to have S-SAD and none SAD (Table 2). When the SAD and S-SAD groups were combined into a winter problem group, and comTable 2 Validity of SPAQ diagnoses. Clinical diagnosis
a
SAD S-SAD Neither SAD nor S-SAD
SPAQ classifications SAD
S-SAD
Neither
5 11 3
6 10 4
0 2 19
Clinical evaluation of individuals, classified by the SPAQ into 3 groups: SAD, S-SAD and neither of these diagnoses. All the subjects came from a community epidemiological study. a DSM-III-R criteria for SAD (American Psychiatric Association, 1987), Kasper et al’s criteria, modified, for S-SAD.
A. Magnusson/
Journal
of Affectioe
Disorders
pared with the randomly selected control group, the SPAQ’s sensitivity and specificity was 94% (CI 80-99%) and 73%, respectively. Assuming a prevalence of 19% for winter problems, the positive predictive value (PPV) for winter problems was 45%. As seen in Table 2, the SPAQ differentiated poorly between SAD and S-SAD, and hence the sensitivity, specificity and positive predictive value for SAD and S-SAD separately were not satisfactory. However, since the SPAQ rarely diagnosed SAD when the clinical diagnosis was neither SAD nor S-SAD and vice versa, the weighted kappa for SAD and S-SAD separately was still 0.44. SAD is a relatively rare condition. It therefore had to be over-represented in Table 3 Psychiatric
diagnoses
of individuals
who were classified The information DIS interviews
Subject No.: DSM-III diagnoses Major depression Bipolar disorder Dysthymic disorder Agoraphobia without panic attacks
1
300.21
Social phobia Generalized anxiety Simple phobia Alcohol abuse Alcohol dependency Amphetamine abuse Amphetamine dependency
300.23 300.02 300.29 305.03 303.93 305.70 304.40
Undifferent. somatoform disorder
300.70
personality
301.40
Hypochondriasis Personality disorder NOS
300.70 301.90
’ b ’ d
Since all the clinically evaluated participants in this study were taken from a community epidemiological survey, it is possible to examine how well the SPAQ predicted prevalences of SAD and S-SAD. In the sample the SPAQ identified 19 individuals with SAD while clinical evaluation found 11. However, only 20 out of the 38 subjects that the SPAQ classified as having S-SAD were evaluated. The rate of SAD in this group was 6/20 (Table 21, and thus
Hospital records b 4
5
6
7
8
9
10
1
11
12
1
1
1
1
1
rate estimations
by the SPAQ to have SAD
1 1
1
1 1
1 1
1
1 1 1
‘d
’
1 1
I I
301.70
O.C. personality disorder
3.2. Prevalence
1
1 1
125
the material. The SPAQ would have a higher specificity (and hence also PPV> in a general population.
d 3
121-129
source from
I
296.33 296.4 300.40 300.22
Panic disorder with agoraphobia
Antisocial disorder
2
40 (1996)
Subjects completed DIS interview. Information available from hospital records and medical doctors, Subjects evaluated by clinical interviews and SIGH-SAD. This individual had not used alcohol for several years.
1
1
1
13
Clinical interviews 14
15
16
17
1
I
1
’ 18
126
A. Magnusson
/ Journal
of Affectice
approximately 5 individuals could be expected to have SAD amongst the remaining 18 individuals not interviewed. Hence the clinical evaluation arrived at a very similar number of SAD subjects as the SPAQ (16 vs. 19). It is unlikely that there would be many cases of SAD amongst those respondents whom the SPAQ had classified as neither having SAD nor S-SAD; in fact, none were found after interviewing 42 subjects from the control groups. Sixteen vs. 19 of 587 subjects are not statistically significant different proportions (c.i. for the difference = -0.025 to 0.03 1). There would have been a 60% chance of detecting a difference at a 95% significance level if the SPAQ estimates had deviated by more than half from the clinical rates. In the study groups, clinical evaluation found 23 subjects with S-SAD where the SPAQ had found 20. However, two out of 21 individuals in the randomly chosen control group had S-SAD according to clinical evaluation. If this proportion (2/21) is extrapolated to the total non-SAD/non-S-SAD sample, the SPAQ has only been able to detect approximately half of the S-SAD cases. In the winter problem group, it was examined whether the rates of S-SAD tapered off as one approaches towards the cut off points for the definition of S-SAD. There was no indication that this occurred. 3.3. Psychiatric
diagnoses
Table 3 shows the psychiatric diagnoses of the SPAQ index cases. Less than half of the subjects obtained a diagnosis of major depressive episode, which is considered an inclusion criterion for SAD in DSM-III-R (American Psychiatric Association, 1987) and DSM-IV (American Psychiatric Association, 1994). It is of interest that 6 of the 11 subjects who had completed the DIS-interview had generalised anxiety disorder. Alcohol abuse and dependency were also commonly diagnosed.
4. Discussion 4.1. Validity of SPAQ classifications The relatively high sensitivity and specificity for winter problems indicate, that the SPAQ was able to
Disorders
40 (1996) 121-129
categorize who was likely to have either SAD or S-SAD versus who was likely to have neither. However, the questionnaire differentiated poorly between SAD and S-SAD, and hence its ability to identify individuals with SAD, was compromised. A diagnosis of a major depressive episode is an inclusion criterion for SAD, and an exclusion criterion for S-SAD (American Psychiatric Association, 1994; Kasper et al., 1988, 1989b). Our experience was that the SPAQ’s content validity and specificity would be considerably improved if it could elicit the criteria for major depressive episode. Such SPAQ versions have indeed recently been developed (Wirz-Justice 1994 and Terman 1994, personal communications). Two years lapsed between the epidemiological study and the clinical interviews. If the two procedures would have been carried out simultaneously, better agreement between the SPAQ and clinical evaluations, might have been obtained. The DSM-III-R (American Psychiatric Association, 1987) and DSM-IV (American Psychiatric Association, 19941 require that it should be established that the seasonal pattern is not caused by recurrent increase in psychosocial stress in winter. Anniversary reactions have also been used as an exclusion criterion for recurrent winter depressions (James et al., 1985). Not a single case was found where the winter symptoms were likely to be caused by increased psychosocial stress in winter or by an anniversary reaction.
4.2. Preualence
estimations
Many individuals with SPAQ classifications of SAD, did not have this diagnosis upon clinical evaluation. However, several individuals, classified by the SPAQ as having S-SAD, had SAD according to clinical evaluation. The result was, that in this study, the SPAQ and clinical evaluation arrived at similar prevalence rates of SAD. To obtain as objective diagnosis as possible, DIS diagnoses of major depressive episode were strictly adhered to. The DIS has the advantage of being more objective than most other diagnostic tools but its disadvantage is that it probes lifetime occurrence of major depressive episodes in a relatively limited fashion (Smith and Weissman, 1991), and it may
A. Magnusson/Journal
ofAffectiL,e
underestimate prevalences of major depressive episodes (Kessler et al., 1994). In this study there was, for example, a patient who had been prescribed antidepressive medication three times by her general practitioner, always in winter. She did not meet DIS criteria for major depressive episode, and we did therefore not classify her as having SAD. The reference standard, the DIS, may in the present study have missed some diagnoses of major depressive episodes and hence SAD. The clinical estimates of SAD rates may thus in this respect be regarded as conservative. In the winter problem group, there was no indication that rates of clinically diagnosed S-SAD tapered off as one approached towards the SPAQ cut off points for S-SAD. Furthermore, two individuals received a S-SAD diagnosis in the group that the SPAQ had classified as neither having SAD or SSAD. Thus, with the current cut off points, the SPAQ may give a conservative estimate of S-SAD. 4.3. Generalizability The present study has an enhanced external validity or generalisability because the participants came from a random sample of the general population. The subjects’ self report might also have been relatively unbiased since they were not a group of self-referred individuals trying to obtain treatment. Longitudinal data were also available for a portion of the sample. Furthermore, since almost all subjects were willing to participate, the group’s composition was little influenced by selection factors. This was, for example, reflected by the participation of individuals with antisocial personality disorder and amphetamine abuse. In spite of all these strengths, the present study is still, like most other studies on SAD, not a prospective study, but the diagnoses rest primarily upon the subjects’ self report and retrospective recall. Retrospective recall of seasonal pattern may be inaccurate (Wicki et al., 1992). 4.4. Construct calidity There has been concern about the construct validity of SAD because several studies have recruited SAD subjects by first describing the putative SAD symptoms (Bauer and Dunner, 1993). This raises the
Disorders
40 (19%)
121-129
127
possibility that the syndrome has been ‘manufactured’ by selection of patients with the expected symptoms (Thompson, 1989). In the present study, a community population was first screened, subsequently SAD was diagnosed in a group of individuals who had not heard of the description of SAD before. This supports the construct validity of the SAD syndrome. On the other hand, several of the SPAQ index cases were found to have generalised anxiety and not mood disorder. That suggests that the seasonal pattern specifier, although valid for mood disorders, might be incomplete, i.e., it might be an appropriate modifier for other psychiatric diagnoses as well. That has indeed been suggested in previous studies (Lam et al., 1991; Marriott et al., 1994; McGrath and Yahia, 1993). Kasper et al. (1988, 1989b) have defined S-SAD by seven criteria. The subjects with S-SAD may not have had a history of major affective disorder in winter time and they may not have sought medical or psychological help for their winter difficulties, nor should the symptoms have disrupted their functioning to a major degree. It was difficult to apply these criteria. There were, for example, individuals in the sample who did not meet the criteria for major depressive episode and hence not SAD, but who had nevertheless regularly sought professional help for their symptoms in winter. In this paper, subjects who had typical SAD symptoms but did not meet the full criteria for major depressive episode, were diagnosed as having S-SAD, even though their winter symptoms had disrupted their functioning or they had sought medical help for their symptoms. Seasonal variation in mood is a continuous dimension in the general population, and SAD and S-SAD appear only to be the extreme form of this (Kasper et al., 1989a). It will therefore be difficult to draw an exact line between the more marked, but normal, seasonal variations in mood vs. milder forms of S-SAD. It may also be difficult to distinguish between mild seasonal variations in mood disorders vs. mild seasonal variations in other psychiatric diseases. 4.5. Psychiatric
diagnoses of SPAQ index cases
The individuals who completed a DIS interview received on the average 3 diagnoses. Such clustering
128
A. Magnusson/Joumal
of Affecrioe Disorders 40 (1996) 121-129
of psychiatric diagnoses is seen in epidemiological studies on psychiatric disorders (Kessler et al., 1994). There were more subjects diagnosed with anxiety disorders than mood disorders by the DIS. Seasonal variation in general anxiety symptoms is the most plausible explanation for these individuals’ marked seasonal variations. However, the SPAQ does not enquire directly about symptoms of generalized anxiety, and thus the findings only indicate that seasonal variations in generalized anxiety do occur. The group with seasonal variation and generalized anxiety was identified by screening a population, thus circumventing the common problem of media recruitment. Alcohol abuse and dependency were also commonly diagnosed in this sample. This could be interpreted as reflecting a subgroup of alcoholics who have marked seasonal variations in their drinking habits or well being. However, the DIS might overrate alcoholism among Icelanders due to peculiar drinking style among youths. The DIS finds very high rates of alcoholism in the Icelandic population (Stefansson, 1994, personal communication), although Iceland has the lowest average per capita consumption of alcohol in Europe (Helgason, 1984). In summary, the SPAQ gave reasonably good prevalence estimates of SAD but a somewhat conservative estimate of S-SAD in this study. The SPAQ was found to be a valid instrument for classifying who has winter problems (SAD or S-SAD) and who has not. However, it discriminated poorly between SAD and S-SAD, and hence did not predict SAD accurately. The construct validity of SAD was supported. However, the SPAQ also identified a group of individuals with generalised anxiety who had marked seasonal variations, suggesting that seasonal pattern specifier is not specific for mood disorders.
Acknowledgements Special thanks to Svein Friis M.D. and Stein Opjordsmoen M.D. for suggestions and critical reading of the manuscript; Eyglo Sigurdardottir for SIGH-SAD ratings, Jon G. Stefansson M.D. for his support and Norman E. Rosenthal M.D. for providing the SPAQ.
References Altman, D.G. (19911 Practical Statistics for Medical Research, 1st Edn. Chapman and Hall, London, UK. American Psychiatric Association (1987) Diagnostic and Statistical Manual of Mental Disorders, 3rd Edn-revised. American Psychiatric Association, Washington, DC. American Psychiatric Association (1994) Diagnostic and Statistical Manual of Mental Disorders, 4th Edn. American Psychiatric Association, Washington, DC. Batter, MS. and Dunner, D.L. (1993) Validity of seasonal pattern as a modifier for recurrent mood disorders for DSM-IV (Review). Compr. Psychiatry 34, 159-170. Booker, J.M. and Hellekson, C.J. (1992) Prevalence of seasonal affective disorder in Alaska. Am. J. Psychiatry 149, 11761182. Dean, A.G., Dean, J.F., Burton, A.H. and Dicker, R.C. (1990) Epi info, Version 5. Centers for Disease Control, Atlanta, GA. Gardner, S.B., Winter, P.J. and Gardner, M.J. (1989) Confidence Interval analysis. Br. Med. J. London, UK. Hardin, T.A., Wehr, T.A., Brewerton, T., Kasper, S., Berrettini, W., Rabkin, J. and Rosenthal, N.E. (19911 Evaluation of seasonality in six clinical populations and two normal populations. J. Psychiatry Res. 25, 75-87. Helgason, T. (1984) Alkoholmisbrugets epidemiologi. Nordisk Med. 99, 290-293. Ito, A., Ichihara, M., Hisanaga, N., Ono, Y., Kayukawa, Y., Ohta, T., Okada, T. and Ozaki, N. (1992) Prevalence of seasonal mood changes in low latitude area: Seasonal Pattern Assessment Questionnaire score of Quezon City workers. Jpn. J. Psychiatry Neurol. 46, 249. James, S.P., Wehr, T.A., Sack, D.A., Parry, B.L. and Rosenthal, N.E. (1985) Treatment of seasonal affective disorder with light in the evening. Br. J. Psychiatry 147, 424-428. Kasper, S., Rogers, S.L., Yancey, A.L., Schulz, P.M., Skwerer, R.G. and Rosenthal, N.E. (1988). Phototherapy in subsyndromal seasonal affective disorder (S-SAD) and ‘diagnosed’ controls. Pharmacopsychiatry 21, 428-429. Kasper, S., Wehr, T.A., Bartko, J.J., Gaist, P.A. and Rosenthal, N.E. (1989a) Epidemiological findings of seasonal changes in mood and behavior. A telephone survey of Montgomery County, Maryland. Arch. Gen. Psychiatry 46, 823-833. Kasper, S., Rogers, S.L., Yancey, A., Schulz, P.M., Skwerer, R.G. and Rosenthal, N.E. (1989b) Phototherapy in individuals with and without subsyndromal seasonal affective disorder. Arch. Gen. Psychiatry 46, 837-844. Kessler, R.C., McGonagle, K.A., Zhao, S., Nelson, C.B., Hughes, M., Eshleman, S., Wittchen, H.U. and Kendler, K.S. (19941 Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey. Arch. Gen. Psychiatry 5 1, 8-19. Lam, R.W., Solyom, L. and Tompkins, A. (1991) Seasonal mood symptoms in bulimia nervosa and seasonal affective disorder. Compr. Psychiatry 32, 552-558. Magnusson, A. and Axelsson, J. (1993) The prevalence of seasonal affective disorder is low among descendants of Icelandic emigrants in Canada. Arch. Gen. Psychiatry 50(12), 947-95 I.
A. Magnusson/Joumal
of Affectice Disorders 40 (19961 121-129
Magnusson, A. and Stefansson, J.G. (1993) Prevalence of seasonal affective disorder in Iceland. Arch. Gen. Psychiatry 50, 941-946. Marriott, P., Greenwood, K. and Armstrong, S.M. (1994) Seasonality in panic disorder. J. Affect. Disord. 3 1, 75-80. McGrath, R.E. and Yahia, M. (1993) Preliminary data on seasonally related alcohol dependence. J. Clin. Psychiatry 54, 260262. Mersch, P.P.A., Middendorp, H., Bouhuys, A.L., Beersma, D.G.M. and Van Den Hoofdakker, R.H. (1995) The prevalence of seasonal affective disorder in the Netherlands. Acta Neuropsychiatr. 7, 47-49. Rosen, L.N., Targum, S.D., Terman, M., Bryant, M.J., Hoffman, H., Kasper, SF., Hamovit, J.R., Docherty, J.P., Welch, B. and Rosenthal, N.E. (1990) Prevalence of seasonal affective disorder at four latitudes. Psychiatry Res. 31, 13 l- 144. Rosenthal, N.E., Sack, D.A., Gillin, J.C., Lewy, A.J., Goodwin, F.K., Davenport, Y _, Mueller, P.S., Newsome, D.A. and Wehr, T.A. (1984). Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy. Arch. Gen. Psychiatry 41, 72-80. Rosenthal, N.E., Genhart, M.J., Sack, D.A., Skwerer, R.G. and Wehr, T.A. (1987) Seasonal affective disorder and its relevance for the understanding and treatment of bulimia. In J.I. Hudson and H.G. Pope (Eds.), The Psychobiology of bulimia. American Psychiatric Press, Washington, DC, pp. 205-228.
129
Smith, A.L. and Weissman, A. (1991) The epidemiology of depressive disorders: national and international perspectives, In J.P. Feighner and W.F. Boyer (Eds.), Diagnoses of Depression. John Wiley&Sons, Chichester, pp. 17-30. Terman, M., Terman, J.S., Quitkin, F.M., McGrath, P.J., Stewart, J.W. and Rafferty. B. (1989) Light therapy for seasonal affective disorder. A review of efficacy. Neuropsychopharmacology 2, l-22. Thompson, C. (1989) The syndrome of seasonal affective disorder. In C. Thompson and T. Silverstone (Eds.), Seasonal Affective Disorder. CNS Publishers, London. pp. 37-57. Thompson, C., Stinson, D., Fernandez, M., Fine, J. and Isaacs, G. (1988) A comparison of normal, bipolar and seasonal affective disorder subjects using the Seasonal Pattern Assessment Questionnaire. J. Affect. Disord. 14, 257-264. Wicki, W., Angst, J. and Merikangas, K.R. (1992) The Zurich Study. XIV. Epidemiology of seasonal depression. Eur. Arch. Psychiatry. Clin. Neurosci. 241, 301-306. Williams, J.B.W., Link, M.J., Rosenthal, N.E. and Terman, M. (1988) Structured Interveiw Guide for the Hamilton Depression Rating Scale Seasonal Affective Disorder Version (SIGHSAD). Biometrics Research Department, Columbia University, New York, NY.
Al#EC’FI
ELSEVIER
DISORDERS
Journal of Affective Disorders 40 (1996) 12 I - I29
Validation of the Seasonal Pattern Assessment Questionnaire ( SPAQ) Andres Magnusson Department of Psychiatry, Received 6 December
Ullrobl
Hospital, 0407 Oslo, Norway
1995; revised 28 March 1996; accepted 28 March 1996
Abstract The validity of the Seasonal Pattern Assessment Questionnaire (SPAQ) was examined by interviewing 81 individuals who had participated in an earlier community survey of seasonal affective disorder (SAD) in Iceland. When SAD and subsyndromal SAD (S-SAD) were combined into a ‘winter problem’ group, the questionnaire’s sensitivity, specificity and positive predictive value for that group were 94%, 73% and 45%, respectively. The SPAQ discriminated poorly between SAD and S-SAD, and hence it had a poor case-finding ability for SAD. Clinical evaluation verified a diagnosis of SAD in individuals who had no previous information about this syndrome. The questionnaire furthermore identified a group of individuals who had generalized anxiety and marked seasonal variations. Clinical evaluation arrived at a similar prevalence rate of SAD as the questionnaire. Keywords: Seasonal affective disorder
; Seasonal Pattern Assessment Questionnaire;
1. Introduction Seasonal Affective Disorder (SAD) is a condition of regularly occurring depression during autumn or winter with remission the following spring or summer (Rosenthal et al., 1984). This disorder causes significant distress, but an effective treatment is available (Terman et al., 1989). A milder form of SAD, termed Subsyndromal Seasonal Affective Disorder (S-SAD), has also been characterized (Kasper et al., 1989b). It is important to have valid instruments to identify the individuals who are likely to suffer from SAD and S-SAD and to be able to estimate the prevalence of these disorders in the 0165-0327/96/$15.00 Copyright PI/ SO165-0327(96)00036-5
Sensitivity;
Specificity;
Anxiety disorder
general population. The Seasonal Pattern Assessment Questionnaire (SPAQ), developed by Rosenthal et al. (1987), is a widely used instrument to screen for SAD. A central feature of the SPAQ is the Seasonality Score index. This index has a good test-retest reliability (Hardin et al., 1991; Thompson et al., 1988). Thompson et al. (1988) and Kasper et al. (1989b) have found that groups of subjects with SAD, S-SAD, major depression without a seasonal pattern, and normal individuals, had significantly different mean scores on the Seasonality Score Index. The Seasonality Score Index has been reported to correlate well with Hamilton Depression Rating Scale scores (Kasper et al., 1989b).
0 1996 Elsevier Science B.V. All rights reserved.
122
A. Magnusson
/ Journal
of Affectire
The SPAQ was originally designed and used as a first line screening instrument, and the index cases were subsequently interviewed and diagnosed clinically. However, in recent years the use of the SPAQ has been extended. Criteria have been developed to identify subjects who are likely to have SAD or S-SAD (Booker and Hellekson, 1992; Kasper et al., 1989a; Magnusson and Axelsson, 1993; Rosen et al., 1990), and the questionnaire has been applied in epidemiological studies of these disorders. Several have already been published (Booker and Hellekson, 1992; Ito et al., 1992; Kasper et al., 1989a; Magnusson and Axelsson, 1993; Magnusson and Stefansson, 1993; Mersch et al., 1995; Rosen et al., 19901, and the questionnaire is presently being used in hitherto unpublished epidemiological studies in Finland, Canada and Norway. This use of the questionnaire requires more stringent validation procedures than have previously been undertaken. We are not aware of any studies that have examined how well the SPAQ estimates prevalences of SAD and S-SAD, and the SPAQ’s sensitivity, specificity and predictive value are, to our knowledge, unknown. The aim of this study was to validate SPAQ classifications of SAD and S-SAD against clinical diagnoses and to examine the SPAQ’s ability to estimate the prevalence of SAD and S-SAD.
2. Methods 2. I. The questionnaire The Seasonal Pattern Assessment Questionnaire (SPAQ) is an instrument for investigating mood and behavioural changes with the seasons. It has several scales. One of these, the Seasonality Score Index (SSI), has six items that measure seasonal variations in mood, appetite, weight, sleep, energy and socialising. The sum of these items is the Seasonality Score (SS), which can range from 0 to 24. Other scales evaluate, for example, the degree to which the seasonal changes are experienced as a problem and in which month of the year the subjects feel best or worst. These three scales are used to classify whether the respondents have SAD, S-SAD or neither of these disorders. The questionnaire was provided by Dr. Norman E. Rosenthal at the National Institute of
Disorders
40 (19961 121-129
Mental Health, USA. It was translated to Icelandic and then back-translated to English to verify accuracy of translation. 2.2. The subjects All 81 clinically evaluated subjects in this study were selected from respondents participating in an earlier community epidemiological study of SAD in Iceland. Iceland is a Nordic country with high educational standards. The procedures of the epidemiological study have been described in detail elsewhere (Magnusson and Stefansson, 1993). Briefly, the SPAQ was mailed to 1000 individuals, randomly selected from the Icelandic National Register in spring 1988. The response rate was 61%. The SPAQ case finding criteria for SAD in the epidemiological study were: An SS of 11 or higher, and experiencing seasonal change as a problem at least to a moderate degree. Furthermore, the subject had to feel worst during one of the winter months. The SPAQ criteria for S-SAD were those of Kasper et al. (1989a): (1) feeling worst in the winter months; (2) a SS of 11 or more; and (3) experiencing seasonal change as a mild problem or no problem at all. Those who had a SS of 9 or 10 and experienced seasonal changes as a problem, at least to a mild degree, were also classified as having S-SAD. These criteria classified 19 individuals as having SAD and 38 individuals with S-SAD in the epidemiological study. In the present study, all those 19 individuals, classified to have SAD in the epidemiological study, were clinically evaluated. Twenty randomly selected individuals from those classified to have S-SAD in the epidemiological study, were also evaluated. Furthermore, two control groups were made up from the respondents of the epidemiological study. One was a contrast group with 21 individuals who reported that their mood and behaviour were virtually unaffected by the seasons. They scored 0 or 1 on the SSI (referred to below as ‘the non-seasonals’). The second control group consisted of 21 individuals who were randomly selected from all the respondents who had not received SPAQ diagnosis of SAD or S-SAD. This latter control group was used in calculations of sensitivity, specificity, predictive value and diagnostic reliability. In the epidemiological study, no cases of Summer SAD were found, hence SAD
A. Magnusson/ Journal ofAffectil,e Disorders 40 (1996) 121-129
refers in this paper to winter SAD. The SAD S-SAD groups combined will be referred to as ‘winter problem group’. After the procedures been fully explained, all participants provided formed consent.
and the had in-
2.3. Ecaluation All 19 subjects who the SPAQ classified as having SAD in the epidemiological study described above, were contacted. They were all willing to participate in the present study. Only one of these dropped out, but a diagnosis of SAD or S-SAD had by then been excluded. Four individuals had been admitted to psychiatric wards. With their consent, information was gathered from hospital records and the diagnostic criteria discussed with their psychiatrists who had followed them over time. These diagnoses were considered superior to a manual diagnosis and they were not further diagnosed. Of the remaining 14 subjects, 11 completed a full Diagnostic Interview Schedule (DIS) interview, administered by a trained person not otherwise involved in the project. The remaining three individuals did not wish to participate in a full DIS evaluation, but were evaluated by a clinical interview, and by SIGH-SAD ratings (described below) in winter. When interviewing those who did not complete the DIS interview, the main focus was on SAD and mood disorders, and no attempt was made to screen for all the diagnoses covered by the DIS. In addition, all 19 subjects were interviewed by the author, and 15 of them were rated by a blind rater on the SIGH-SAD in winter. If the subjects had previously contacted psychiatrists or general practitioners for psychiatric problems, information was collected from these sources with the patients’ consent. The S-SAD group, the non-seasonal group, and the randomly chosen control group, were evaluated for symptoms of SAD by a clinical interview. The mood disorder part of the DIS was administered to obtain an objective diagnosis of SAD. A blind rater attempted to rate the participants in winter on the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version (SIGH-SAD). This is a structured interview guide which incorporates the Hamilton Depression Rating Scale and 8 additional items
123
that evaluate the atypical depressive symptoms of SAD (Williams et al., 1988). The SAD group and the non-seasonals were contacted between 15th December 1990 and 15th February 1991. Most of the SAD subjects felt that they were within their difficult winter period at the time of rating. The S-SAD group was reached between 15th February and 15th March. By that time, all but four of the subjects felt that their winter symptoms were already starting to wane or had disappeared. The reference standard was the application of the DSM-III-R criteria for SAD (American Psychiatric Association, 19871, using all available information, and adhering to the DIS or hospital chart diagnosis of a major depressive episode. S-SAD has been defined by Kasper et al. (1988, 1989b). In the present study, the reference standard for S-SAD was a clinical application of Kaspefs criteria, slightly modified as discussed below. To assess diagnostic reliability, a psychiatrist not otherwise involved in this project evaluated blindly the data from 24 subjects, 8 of whom the SPAQ had classified as SAD, 8 as S-SAD and 8 subjects chosen randomly from the individuals classified neither to have SAD or S-SAD. The kappa value for these 3 diagnostic groups was 0.8 I. 2.4. Statistics Sensitivity, specificity, positive predictive value and weighted kappa were calculated as described in Altman’s Practical Statistics for Medical Research (Altman, 199 1). The non-seasonal group was excluded from these analyses, since their inclusion would have given an artificially high specificity and positive predictive value. Confidence interval (exact test) was calculated by the Confidence Interval Analysis computer program (Gardner et al., 1989). Power for statistical tests was calculated by the Epi info version 5.1 computer program (Dean et al., 1990)
3. Results 3. I. Validation of SPAQ classifications When the subjects classified as having SAD or S-SAD by the SPAQ were interviewed, all except
A. Magnusson/Joumal
124 Table 1 Winter symptoms
of Affective Disorders 40 (1996) 121-129
in relation to SPAQ classifications. SPAQ classifications SAD
n
Sex M/F Mean age (years) Symptoms in the winter: Depressed mood, dysphory Lack of energy Mean increase in sleep duration, min (SD) Mean increase in body weight, kg (SD) Mean SIGH-SAD scores in winter ’ (SD) Psychosocial stress more: in winter(W) in summer(S) Winter symptoms occur regularly The symptoms lift in the summer A major depressive episode Results from the seasons. a No specific b Individuals ’ II = 15 for
S-SAD
Non-seasonals
20 6/14 34.5
21 13/8 41.1
83% 89% 123 (971 1.6 (2.6) 17.3 (11.2) W=l
75% 55% 59 (611 1.7 (2.1) 4.0 (3.1) w=2 s=2
_a _a
100% 84% 8
95% 85% 8
19 10/9 33.8
clinical interviews with subjects who the SPAQ had classified
b
1.2 (17) 0 1.8 (3.4) w=4 s=5 0% _a 3
into 3 groups: SAD, S-SAD and subjects virtually unaffected
by
winter symptoms. in this group had a Seasonality score of 0 or 1. SAD, 18 for S-SAD and 21 for non-seasonals.
one said that their winter symptoms recurred regularly. Most of these subjects also felt that their symptoms remitted fully in the summer (Table 1). The mean SIGH-SAD score in the S-SAD group was significantly different from both the SAD group (t-test, t = 4.46, P < 0.001) and the non-seasonals (t-test, t = 2.12, P < 0.05). No individuals were found whose symptoms of SAD or S-SAD could be accounted for by seasonal variation in psychosocial stress or anniversary reaction. A major depressive episode is considered a prerequisite for a diagnosis of SAD. Of the 81 individuals studied, 19 had experienced a major depressive episode. Three of these belonged to the non-seasonals and their depression had no relation to seasons. In the winter problem group, there were 5 subjects who could not be given a clinical diagnosis of SAD although they had experienced a major depressive episode. These were the individuals who generally had the most severe depression in the sample. Although they felt that their symptoms did improve substantially or disappear during the summer, records from hospitals and private psychiatrists
could not confirm this, The remaining 11 subjects with major depressive episodes were given a clinical diagnosis of SAD. Only two individuals, whom the SPAQ had classified as having winter problems, had upon clinical evaluation too mild symptoms to warrant a diagnosis of SAD or S-SAD. In the randomly chosen control group, two subjects were diagnosed to have S-SAD and none SAD (Table 2). When the SAD and S-SAD groups were combined into a winter problem group, and comTable 2 Validity of SPAQ diagnoses. Clinical diagnosis
a
SAD S-SAD Neither SAD nor S-SAD
SPAQ classifications SAD
S-SAD
Neither
5 11 3
6 10 4
0 2 19
Clinical evaluation of individuals, classified by the SPAQ into 3 groups: SAD, S-SAD and neither of these diagnoses. All the subjects came from a community epidemiological study. a DSM-III-R criteria for SAD (American Psychiatric Association, 1987), Kasper et al’s criteria, modified, for S-SAD.
A. Magnusson/
Journal
of Affectioe
Disorders
pared with the randomly selected control group, the SPAQ’s sensitivity and specificity was 94% (CI 80-99%) and 73%, respectively. Assuming a prevalence of 19% for winter problems, the positive predictive value (PPV) for winter problems was 45%. As seen in Table 2, the SPAQ differentiated poorly between SAD and S-SAD, and hence the sensitivity, specificity and positive predictive value for SAD and S-SAD separately were not satisfactory. However, since the SPAQ rarely diagnosed SAD when the clinical diagnosis was neither SAD nor S-SAD and vice versa, the weighted kappa for SAD and S-SAD separately was still 0.44. SAD is a relatively rare condition. It therefore had to be over-represented in Table 3 Psychiatric
diagnoses
of individuals
who were classified The information DIS interviews
Subject No.: DSM-III diagnoses Major depression Bipolar disorder Dysthymic disorder Agoraphobia without panic attacks
1
300.21
Social phobia Generalized anxiety Simple phobia Alcohol abuse Alcohol dependency Amphetamine abuse Amphetamine dependency
300.23 300.02 300.29 305.03 303.93 305.70 304.40
Undifferent. somatoform disorder
300.70
personality
301.40
Hypochondriasis Personality disorder NOS
300.70 301.90
’ b ’ d
Since all the clinically evaluated participants in this study were taken from a community epidemiological survey, it is possible to examine how well the SPAQ predicted prevalences of SAD and S-SAD. In the sample the SPAQ identified 19 individuals with SAD while clinical evaluation found 11. However, only 20 out of the 38 subjects that the SPAQ classified as having S-SAD were evaluated. The rate of SAD in this group was 6/20 (Table 21, and thus
Hospital records b 4
5
6
7
8
9
10
1
11
12
1
1
1
1
1
rate estimations
by the SPAQ to have SAD
1 1
1
1 1
1 1
1
1 1 1
‘d
’
1 1
I I
301.70
O.C. personality disorder
3.2. Prevalence
1
1 1
125
the material. The SPAQ would have a higher specificity (and hence also PPV> in a general population.
d 3
121-129
source from
I
296.33 296.4 300.40 300.22
Panic disorder with agoraphobia
Antisocial disorder
2
40 (1996)
Subjects completed DIS interview. Information available from hospital records and medical doctors, Subjects evaluated by clinical interviews and SIGH-SAD. This individual had not used alcohol for several years.
1
1
1
13
Clinical interviews 14
15
16
17
1
I
1
’ 18
126
A. Magnusson
/ Journal
of Affectice
approximately 5 individuals could be expected to have SAD amongst the remaining 18 individuals not interviewed. Hence the clinical evaluation arrived at a very similar number of SAD subjects as the SPAQ (16 vs. 19). It is unlikely that there would be many cases of SAD amongst those respondents whom the SPAQ had classified as neither having SAD nor S-SAD; in fact, none were found after interviewing 42 subjects from the control groups. Sixteen vs. 19 of 587 subjects are not statistically significant different proportions (c.i. for the difference = -0.025 to 0.03 1). There would have been a 60% chance of detecting a difference at a 95% significance level if the SPAQ estimates had deviated by more than half from the clinical rates. In the study groups, clinical evaluation found 23 subjects with S-SAD where the SPAQ had found 20. However, two out of 21 individuals in the randomly chosen control group had S-SAD according to clinical evaluation. If this proportion (2/21) is extrapolated to the total non-SAD/non-S-SAD sample, the SPAQ has only been able to detect approximately half of the S-SAD cases. In the winter problem group, it was examined whether the rates of S-SAD tapered off as one approaches towards the cut off points for the definition of S-SAD. There was no indication that this occurred. 3.3. Psychiatric
diagnoses
Table 3 shows the psychiatric diagnoses of the SPAQ index cases. Less than half of the subjects obtained a diagnosis of major depressive episode, which is considered an inclusion criterion for SAD in DSM-III-R (American Psychiatric Association, 1987) and DSM-IV (American Psychiatric Association, 1994). It is of interest that 6 of the 11 subjects who had completed the DIS-interview had generalised anxiety disorder. Alcohol abuse and dependency were also commonly diagnosed.
4. Discussion 4.1. Validity of SPAQ classifications The relatively high sensitivity and specificity for winter problems indicate, that the SPAQ was able to
Disorders
40 (1996) 121-129
categorize who was likely to have either SAD or S-SAD versus who was likely to have neither. However, the questionnaire differentiated poorly between SAD and S-SAD, and hence its ability to identify individuals with SAD, was compromised. A diagnosis of a major depressive episode is an inclusion criterion for SAD, and an exclusion criterion for S-SAD (American Psychiatric Association, 1994; Kasper et al., 1988, 1989b). Our experience was that the SPAQ’s content validity and specificity would be considerably improved if it could elicit the criteria for major depressive episode. Such SPAQ versions have indeed recently been developed (Wirz-Justice 1994 and Terman 1994, personal communications). Two years lapsed between the epidemiological study and the clinical interviews. If the two procedures would have been carried out simultaneously, better agreement between the SPAQ and clinical evaluations, might have been obtained. The DSM-III-R (American Psychiatric Association, 1987) and DSM-IV (American Psychiatric Association, 19941 require that it should be established that the seasonal pattern is not caused by recurrent increase in psychosocial stress in winter. Anniversary reactions have also been used as an exclusion criterion for recurrent winter depressions (James et al., 1985). Not a single case was found where the winter symptoms were likely to be caused by increased psychosocial stress in winter or by an anniversary reaction.
4.2. Preualence
estimations
Many individuals with SPAQ classifications of SAD, did not have this diagnosis upon clinical evaluation. However, several individuals, classified by the SPAQ as having S-SAD, had SAD according to clinical evaluation. The result was, that in this study, the SPAQ and clinical evaluation arrived at similar prevalence rates of SAD. To obtain as objective diagnosis as possible, DIS diagnoses of major depressive episode were strictly adhered to. The DIS has the advantage of being more objective than most other diagnostic tools but its disadvantage is that it probes lifetime occurrence of major depressive episodes in a relatively limited fashion (Smith and Weissman, 1991), and it may
A. Magnusson/Journal
ofAffectiL,e
underestimate prevalences of major depressive episodes (Kessler et al., 1994). In this study there was, for example, a patient who had been prescribed antidepressive medication three times by her general practitioner, always in winter. She did not meet DIS criteria for major depressive episode, and we did therefore not classify her as having SAD. The reference standard, the DIS, may in the present study have missed some diagnoses of major depressive episodes and hence SAD. The clinical estimates of SAD rates may thus in this respect be regarded as conservative. In the winter problem group, there was no indication that rates of clinically diagnosed S-SAD tapered off as one approached towards the SPAQ cut off points for S-SAD. Furthermore, two individuals received a S-SAD diagnosis in the group that the SPAQ had classified as neither having SAD or SSAD. Thus, with the current cut off points, the SPAQ may give a conservative estimate of S-SAD. 4.3. Generalizability The present study has an enhanced external validity or generalisability because the participants came from a random sample of the general population. The subjects’ self report might also have been relatively unbiased since they were not a group of self-referred individuals trying to obtain treatment. Longitudinal data were also available for a portion of the sample. Furthermore, since almost all subjects were willing to participate, the group’s composition was little influenced by selection factors. This was, for example, reflected by the participation of individuals with antisocial personality disorder and amphetamine abuse. In spite of all these strengths, the present study is still, like most other studies on SAD, not a prospective study, but the diagnoses rest primarily upon the subjects’ self report and retrospective recall. Retrospective recall of seasonal pattern may be inaccurate (Wicki et al., 1992). 4.4. Construct calidity There has been concern about the construct validity of SAD because several studies have recruited SAD subjects by first describing the putative SAD symptoms (Bauer and Dunner, 1993). This raises the
Disorders
40 (19%)
121-129
127
possibility that the syndrome has been ‘manufactured’ by selection of patients with the expected symptoms (Thompson, 1989). In the present study, a community population was first screened, subsequently SAD was diagnosed in a group of individuals who had not heard of the description of SAD before. This supports the construct validity of the SAD syndrome. On the other hand, several of the SPAQ index cases were found to have generalised anxiety and not mood disorder. That suggests that the seasonal pattern specifier, although valid for mood disorders, might be incomplete, i.e., it might be an appropriate modifier for other psychiatric diagnoses as well. That has indeed been suggested in previous studies (Lam et al., 1991; Marriott et al., 1994; McGrath and Yahia, 1993). Kasper et al. (1988, 1989b) have defined S-SAD by seven criteria. The subjects with S-SAD may not have had a history of major affective disorder in winter time and they may not have sought medical or psychological help for their winter difficulties, nor should the symptoms have disrupted their functioning to a major degree. It was difficult to apply these criteria. There were, for example, individuals in the sample who did not meet the criteria for major depressive episode and hence not SAD, but who had nevertheless regularly sought professional help for their symptoms in winter. In this paper, subjects who had typical SAD symptoms but did not meet the full criteria for major depressive episode, were diagnosed as having S-SAD, even though their winter symptoms had disrupted their functioning or they had sought medical help for their symptoms. Seasonal variation in mood is a continuous dimension in the general population, and SAD and S-SAD appear only to be the extreme form of this (Kasper et al., 1989a). It will therefore be difficult to draw an exact line between the more marked, but normal, seasonal variations in mood vs. milder forms of S-SAD. It may also be difficult to distinguish between mild seasonal variations in mood disorders vs. mild seasonal variations in other psychiatric diseases. 4.5. Psychiatric
diagnoses of SPAQ index cases
The individuals who completed a DIS interview received on the average 3 diagnoses. Such clustering
128
A. Magnusson/Joumal
of Affecrioe Disorders 40 (1996) 121-129
of psychiatric diagnoses is seen in epidemiological studies on psychiatric disorders (Kessler et al., 1994). There were more subjects diagnosed with anxiety disorders than mood disorders by the DIS. Seasonal variation in general anxiety symptoms is the most plausible explanation for these individuals’ marked seasonal variations. However, the SPAQ does not enquire directly about symptoms of generalized anxiety, and thus the findings only indicate that seasonal variations in generalized anxiety do occur. The group with seasonal variation and generalized anxiety was identified by screening a population, thus circumventing the common problem of media recruitment. Alcohol abuse and dependency were also commonly diagnosed in this sample. This could be interpreted as reflecting a subgroup of alcoholics who have marked seasonal variations in their drinking habits or well being. However, the DIS might overrate alcoholism among Icelanders due to peculiar drinking style among youths. The DIS finds very high rates of alcoholism in the Icelandic population (Stefansson, 1994, personal communication), although Iceland has the lowest average per capita consumption of alcohol in Europe (Helgason, 1984). In summary, the SPAQ gave reasonably good prevalence estimates of SAD but a somewhat conservative estimate of S-SAD in this study. The SPAQ was found to be a valid instrument for classifying who has winter problems (SAD or S-SAD) and who has not. However, it discriminated poorly between SAD and S-SAD, and hence did not predict SAD accurately. The construct validity of SAD was supported. However, the SPAQ also identified a group of individuals with generalised anxiety who had marked seasonal variations, suggesting that seasonal pattern specifier is not specific for mood disorders.
Acknowledgements Special thanks to Svein Friis M.D. and Stein Opjordsmoen M.D. for suggestions and critical reading of the manuscript; Eyglo Sigurdardottir for SIGH-SAD ratings, Jon G. Stefansson M.D. for his support and Norman E. Rosenthal M.D. for providing the SPAQ.
References Altman, D.G. (19911 Practical Statistics for Medical Research, 1st Edn. Chapman and Hall, London, UK. American Psychiatric Association (1987) Diagnostic and Statistical Manual of Mental Disorders, 3rd Edn-revised. American Psychiatric Association, Washington, DC. American Psychiatric Association (1994) Diagnostic and Statistical Manual of Mental Disorders, 4th Edn. American Psychiatric Association, Washington, DC. Batter, MS. and Dunner, D.L. (1993) Validity of seasonal pattern as a modifier for recurrent mood disorders for DSM-IV (Review). Compr. Psychiatry 34, 159-170. Booker, J.M. and Hellekson, C.J. (1992) Prevalence of seasonal affective disorder in Alaska. Am. J. Psychiatry 149, 11761182. Dean, A.G., Dean, J.F., Burton, A.H. and Dicker, R.C. (1990) Epi info, Version 5. Centers for Disease Control, Atlanta, GA. Gardner, S.B., Winter, P.J. and Gardner, M.J. (1989) Confidence Interval analysis. Br. Med. J. London, UK. Hardin, T.A., Wehr, T.A., Brewerton, T., Kasper, S., Berrettini, W., Rabkin, J. and Rosenthal, N.E. (19911 Evaluation of seasonality in six clinical populations and two normal populations. J. Psychiatry Res. 25, 75-87. Helgason, T. (1984) Alkoholmisbrugets epidemiologi. Nordisk Med. 99, 290-293. Ito, A., Ichihara, M., Hisanaga, N., Ono, Y., Kayukawa, Y., Ohta, T., Okada, T. and Ozaki, N. (1992) Prevalence of seasonal mood changes in low latitude area: Seasonal Pattern Assessment Questionnaire score of Quezon City workers. Jpn. J. Psychiatry Neurol. 46, 249. James, S.P., Wehr, T.A., Sack, D.A., Parry, B.L. and Rosenthal, N.E. (1985) Treatment of seasonal affective disorder with light in the evening. Br. J. Psychiatry 147, 424-428. Kasper, S., Rogers, S.L., Yancey, A.L., Schulz, P.M., Skwerer, R.G. and Rosenthal, N.E. (1988). Phototherapy in subsyndromal seasonal affective disorder (S-SAD) and ‘diagnosed’ controls. Pharmacopsychiatry 21, 428-429. Kasper, S., Wehr, T.A., Bartko, J.J., Gaist, P.A. and Rosenthal, N.E. (1989a) Epidemiological findings of seasonal changes in mood and behavior. A telephone survey of Montgomery County, Maryland. Arch. Gen. Psychiatry 46, 823-833. Kasper, S., Rogers, S.L., Yancey, A., Schulz, P.M., Skwerer, R.G. and Rosenthal, N.E. (1989b) Phototherapy in individuals with and without subsyndromal seasonal affective disorder. Arch. Gen. Psychiatry 46, 837-844. Kessler, R.C., McGonagle, K.A., Zhao, S., Nelson, C.B., Hughes, M., Eshleman, S., Wittchen, H.U. and Kendler, K.S. (19941 Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey. Arch. Gen. Psychiatry 5 1, 8-19. Lam, R.W., Solyom, L. and Tompkins, A. (1991) Seasonal mood symptoms in bulimia nervosa and seasonal affective disorder. Compr. Psychiatry 32, 552-558. Magnusson, A. and Axelsson, J. (1993) The prevalence of seasonal affective disorder is low among descendants of Icelandic emigrants in Canada. Arch. Gen. Psychiatry 50(12), 947-95 I.
A. Magnusson/Joumal
of Affectice Disorders 40 (19961 121-129
Magnusson, A. and Stefansson, J.G. (1993) Prevalence of seasonal affective disorder in Iceland. Arch. Gen. Psychiatry 50, 941-946. Marriott, P., Greenwood, K. and Armstrong, S.M. (1994) Seasonality in panic disorder. J. Affect. Disord. 3 1, 75-80. McGrath, R.E. and Yahia, M. (1993) Preliminary data on seasonally related alcohol dependence. J. Clin. Psychiatry 54, 260262. Mersch, P.P.A., Middendorp, H., Bouhuys, A.L., Beersma, D.G.M. and Van Den Hoofdakker, R.H. (1995) The prevalence of seasonal affective disorder in the Netherlands. Acta Neuropsychiatr. 7, 47-49. Rosen, L.N., Targum, S.D., Terman, M., Bryant, M.J., Hoffman, H., Kasper, SF., Hamovit, J.R., Docherty, J.P., Welch, B. and Rosenthal, N.E. (1990) Prevalence of seasonal affective disorder at four latitudes. Psychiatry Res. 31, 13 l- 144. Rosenthal, N.E., Sack, D.A., Gillin, J.C., Lewy, A.J., Goodwin, F.K., Davenport, Y _, Mueller, P.S., Newsome, D.A. and Wehr, T.A. (1984). Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy. Arch. Gen. Psychiatry 41, 72-80. Rosenthal, N.E., Genhart, M.J., Sack, D.A., Skwerer, R.G. and Wehr, T.A. (1987) Seasonal affective disorder and its relevance for the understanding and treatment of bulimia. In J.I. Hudson and H.G. Pope (Eds.), The Psychobiology of bulimia. American Psychiatric Press, Washington, DC, pp. 205-228.
129
Smith, A.L. and Weissman, A. (1991) The epidemiology of depressive disorders: national and international perspectives, In J.P. Feighner and W.F. Boyer (Eds.), Diagnoses of Depression. John Wiley&Sons, Chichester, pp. 17-30. Terman, M., Terman, J.S., Quitkin, F.M., McGrath, P.J., Stewart, J.W. and Rafferty. B. (1989) Light therapy for seasonal affective disorder. A review of efficacy. Neuropsychopharmacology 2, l-22. Thompson, C. (1989) The syndrome of seasonal affective disorder. In C. Thompson and T. Silverstone (Eds.), Seasonal Affective Disorder. CNS Publishers, London. pp. 37-57. Thompson, C., Stinson, D., Fernandez, M., Fine, J. and Isaacs, G. (1988) A comparison of normal, bipolar and seasonal affective disorder subjects using the Seasonal Pattern Assessment Questionnaire. J. Affect. Disord. 14, 257-264. Wicki, W., Angst, J. and Merikangas, K.R. (1992) The Zurich Study. XIV. Epidemiology of seasonal depression. Eur. Arch. Psychiatry. Clin. Neurosci. 241, 301-306. Williams, J.B.W., Link, M.J., Rosenthal, N.E. and Terman, M. (1988) Structured Interveiw Guide for the Hamilton Depression Rating Scale Seasonal Affective Disorder Version (SIGHSAD). Biometrics Research Department, Columbia University, New York, NY.