Measuring disability in subjects with anxiety disorders

Eur Psychiato' 1997;12 (Suppl 3):249s-253s

© Elsevier, Paris

Measuring disability in subjects with anxiety disorders* M Placchi UCB SA Pharma Sector. R&D, Chemin du Foriest, B - 1420 Braine-l'Alleud, Belgium

Summary - Subjects with anxiety disorders display substantial disabilities in health-related quality of life. The Sheehan Disability Scale (SDS) and SF-36 Questionnaire (SF-36) have been administered to subjects with anxiety disorders participating in psychopharmacology clinical trials and observational studies to evaluate their impaired functioning. The SDS does not address and does not include all the disabilities important to subjects with anxiety disorders and susceptible to being affected by drugs with anxiolytic effects, all of which are associated with significant problems. As a single-state-in-time rating, the SDS is often inadequate to discern subtle, but important,changes which may occur between measurements. The SF-36 as a measure of health status can, on the other hand, assess only the patient's behavior most directly affected by the disorder and treatment. As a result, the SF-36 enables the differentiation of functioning and well-being of subjects with anxiety disorders from diverse populations. There is little documentary evidence that demonstrates the value and actual performance of the SDS and SF-36 for the intended purpose. In the absence of a general consensus concerning operational definition, the measurement of disability in this patient population with these scales may be obsolete. There is the need for more specific and simple instruments capable to assess the distinct pattern of impairment associated with subjects with anxiety disorders. anxiety disorders / disability / Sheehan Disability Scale / SF-36 questionnaire

INTRODUCTION A c c o r d i n g to the World Health O r g a n i z a t i o n ' s International Classification of Impairments, Disabilities, and Handicaps (World Health Organization, 1980), disabilities are defined as "restrictions or lack of ability to perform an activity in a m a n n e r or within the range considered normal for a h u m a n being". The Diagnostic and Statistical M a n u a l ( D S M ) - I V (American Psychiatric Association, 1994) definition of a mental disorder embodies disability as an important aspect of the disease. "In D S M - I V , each of the mental disorders is conceptualized as a clinically significant behavioral or psychological s y n d r o m e or pattern that occurs in an individual and that is associated with present distress (eg, a painful symptom) or disability (ie, impairment in one or more important areas of functioning) or with a significantly increased risk of suffering death, pain, disability, or an important loss of freedom". * The opinions expressed in this report are those of the author and are not necessary shared by UCB SA Pharma Sector.

The D S M - I V introduces the Global A s s e s s m e n t of F u n c t i o n i n g (GAF) Scale to assess the individual with respect only to psychological, social and occupational functioning. O n e difficulty in G A F scoring is that assessment of functioning according to Axis V is attributed to mental i m p a i r m e n t alone and that a single rating c o m b i n e s measures of psychological, social and occupational functioning. In addition, Axis V appears to be a reasonably valid measure of psychiatric disturbance but with a modest interrater reliability ( B o d l u n d et al, 1994). In psychopharmacology clinical trials and observational studies there has been a tendency to assess the f u n c t i o n i n g of subjects with anxiety disorders indirectly from measures of s y m p t o m severity, n a m e l y Clinical Global Impression (Guy, 1976) and H a m i l t o n Anxiety Rating Scale (Hamilton, 1959). G i v e n that the individual's level of functioning holds crucial information for treatment decision m a k i n g and predicting outcome, clinicians and researchers need reliable and validated measures of the pattern of impairment. There are a small n u m b e r of disability scales for

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Table I. Findings on quality of life in subjects with anxiety disorders. Article

Source

Markowitz et al, 1989 Datafrom EpidemiologicalCatchment Area Study* Massion et al, 1993

Warshaw et al, 1993 Leon et al, 1995

Results

"A lifetime Diagnostic Interview Schedule/DSM-lll diagnosis of panic disorder was associated with pervasive social and health consequences similar to or greater than those associated with major depression". "There was a high degree of coexistence of anxiety disordersand major depressivedisorder.Subjectswith generalizedanxietydisorder... had the worst emotional health rating. Subjects with panic disorder withoutagoraphobiahad the mostlikelihoodof a historyof alcoholabuse". "Subjects with post-traumaticstress disorder had the worst functioning on all of the measures examined except social life".

357 subjects with DSM-III-R diagnosed panic disorder and/or generalized anxiety disorder in a prospective, naturalistic, longitudinal, multicenter study 711 subjects with DSM-III-R-defined anxiety disorders in a prospective, naturalistic, longitudinal multicenter study Data from EpidemiologicalCatchment "Men with panic disorder, phobias or obsessive-compulsivedisorder Area Study* in the previous six months are more likely to be chronically unemployed and to receive disability or welfare".

*Surveyed over 18,000 adults living in five United States communities.

which reliability and validity have been investigated and have gained some acceptance in clinical research. This paper focuses mainly on two instruments: the Sheehan Disability Scale (SDS) (Sheehan, 1983) and SF-36 Questionnaire (SF-36) (Ware, 1993). Other aims include evaluation of how suitable these instruments are to assess disability in subjects with anxiety disorders. Q U A L I T Y O F L I F E IN S U B J E C T S

WITH ANXIETY DISORDERS The psychological and social concomitants associated with subjects with anxiety disorders and the impact of which has been conceptually included under the rubric of quality of life have been examined in a number of articles (table I), Hence, the measurement of functioning and wellbeing in subjects with anxiety disorders aims at achieving a more comprehensive content of evaluation of the disorder/treatment effects. If, in addition, it is very important within the diagnosis of anxiety disorders to differentiate between Disability and Well-being (between mental and social well-being versus physical wellbeing), Disability is to be rated with instruments other than those intended for general health outcomes. I N S T R U M E N T S U S E D T O REPORT O V E R A L L F U N C T I O N I N G IN S U B J E C T S WITH ANXIETY DISORDERS A variety of instruments (Massion et al, 1993; Warshaw et al, 1993; Leon et al, 1992; Davidson JRT, 1995, personal communication) have been employed either alone or in combination to evaluate overall functioning in subjects with anxiety disorders. These instruments

include selected items from Yale Greater New Haven Health Survey-Community Interview-Wave 1; Quality Of Life Items from Longitudinal Interval Follow-Up Evaluation; Sheehan Disability Scale; SF-36 Questionnaire. The investigators from the selected articles neither conceptually identified what they meant by impaired functioning nor justified their reasons for choosing the particular instruments used in their research. Only the SDS (Sheehan, 1983) was designed to assess impaired functioning in subjects with anxiety disorders. The SF-36 (Ware, 1993) and Yale Greater New Haven H e a l t h - C o m m u n i t y I n t e r v i e w - W a v e 1 (Myers, 1980) are generic measures of health status, while the Longitudinal Interval Follow-Up Evaluation (Keller et al, 1987) is an integrated system for assessing the longitudinal course of psychiatric disorders. Tables II and III show the item content and organization o f the SDS and SF-36. The psychometric properties of the SDS have been examined with the measures obtained from two independent clinical trials, one of which was performed in 476 subjects meeting the DSM-III-R criteria for panic disorder and the other in 122 subjects meeting the DSM-III-R criteria for both panic disorder and depresTable I1. SDS: items and organization. Se!f-rated scale with three Likert (0-10) items

To what extent do your symptoms impair your functioning in: a) your social life b) your family/home life c) your work life

Item's anchor points

Estimated time to complete

one minute None Moderately Severely

Measuring disability in subjects with anxiety disorder

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Table III. SF-36: items and organisation. Self-rated multi-item scale in eight domains of health status and well-being

Physical functioning Role limitations due to physical health problems Bodily pain General health perceptions Vitality (energy/fatigue) Social functioning Role limitations due to emotional problems Mental health (psychological distress and psychologicalwell-being)

Domain's scores to be computed and tran.~[brmed on to a scale

Estimated time to complete

0 (worst) - 100 (best)

five minutes

sion (Leon et al, 1992). Both the SDS and SF-36 have been administered to subjects with social phobia (Davidson JRT 1995, personal communication). Table IV lists the C r o n b a c h ' s coefficient alphas (Cronbach, 1951) computed, within each study, for the pooled sample pre-treatment and for each medication group post-treatment. A Cronbach's coefficient alpha exceeding 0.80 is considered an acceptable index of reliability for internal consistency among an instrument's items. Therefore the SDS, whose three highlyinterrelated items cannot estimate all the parameters characterizing a patient's disability, appeared to be a moderately reliable measure of impaired functioning, particularly when applied to patients meeting the criteria for panic disorder without comorbid depression. The SDS was sensitive to a treatment intervention changing impaired functioning, as demonstrated by the significantly lower means of the SDS items obtained after treatment for each group in both studies (Leon et al, 1992). Another trial with 75 patients fulfilling the DSM-III-R criteria for social phobia (Davidson et al, 1993) also showed a time-effect for both the tested treatments (clonazepam and placebo) in respect to each item of the SDS. However, this time-effect was statistically significant only for two of the three disability measures in the drug treatment group. At present there are no published data from repeated administrations of the SF-36 to subjects with anxiety T a b l e I V . S D S : Cronbach's

Pre-treatment Pooled

disorders. Estimates of score reliability for the SF-36 scales have been obtained from 14 studies (n = 30,914) performed across various samples (Ware, 1993). For each scale, the median of the reliability coefficients though not all the authors used the same method- equals or exceeds 0.80 except for the Social Functioning scale (0.76). These estimates meet accepted standards of reliability for measures used in group analyses, but do not achieve the values [> 0.90] required for comparisons of health status among individuals or across administrations to the same individual. DISCUSSION M e a s u r i n g d i s a b i l i t y , as s e p a r a t e from a b n o r m a l symptoms and thoughts, in psychiatric patients requires decisions about which phenomena are to be included as input, how to rate each phenomenon, and how to aggregate the diverse individual ratings into a single output citation (Feinstein et ai, 1986). In literature, the definition of disability associated with persons under 65 years of age is often broader than the disability definition of the World Health Organization (Spector, 1996). The assessment of disability is affected by all of the personal factors, including the patient's effort and others' support in the performance (Feinstein, 1986), and especially the patient's expectations regarding health,

coefficient alphas. Alprazolam

Post-treaonent lmipramine

Placebo

Cross National Collaborative Panic Stud)': 8 Weelc~

0. 74 (n = 476)

0.85 (n = 203)

-

0.86 (n = 129)

Panic Depression Stucly: At 8 Weeks

0. 56 (n = 122) Source: Leon et al, 1992.

0. 77 (n = 35)

0.83 (n = 34)

0.64 (n = 27)

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and ability to cope with limitations and disability (Testa and Simonson, 1996). Self-report scales are simple to administer and remove any bias that the interviewer can enter in the interview situation (Weissman and Bothwell, 1976). Usually the investigators look for scales whose reliability and validity have already been established. In the absence of a general consensus concerning the operational definition of disability associated with different mental disorders, the choice of the SDS and SF36 appears to suitably represent the domains of impaired functioning in subjects with anxiety disorders. However, in addition to the statistical coefficients for quantitative reliability, the qualitative attributes for clinical sensibility are to be considered carefully prior to using these scales in this patient population. The SDS does not address and does not include all the disabilities important to subjects with anxiety disorders and susceptible to being affected by drugs with anxiolytic effects, all of which are associated with significant problems. For example, the majority of benzodiazepine users claim continued satisfaction with the drug-effects over long periods of time. With chronic use, the therapeutic effects of benzodiazepines on anxiety states persist as does the memory impairment (Golombok et al, 1988; Curran, 1992) for those populations with compromised cognitive function, especially the elderly. The SDS rates a patient's condition at a single state in time, which is often inadequate to discern subtle but important changes which may occur between measurements. The comparison of single-state values may not sensitively detect small changes in daily activities, such as those associated with impaired cognitive function. A finer discrimination requires additional unambiguously-defined categories with more specific anchor points than the present ones, so that the quantity being measured can be interpreted more exactly. Finally, the SDS has shown an acceptable reliability only in subjects with panic disorder and its psychometric properties need to be examined in patients with other anxiety syndromes. The SF-36 as a measure of health status can on the other hand assess only the patient's behavior most directly affected by the anxiety disorder and treatment. As a result, the SF-36 enables differentiation of the functioning and well-being of subjects with anxiety disorders from diverse populations. However, the ability and validity of the SF-36 to describe groups of subjects with different anxiety disorders are to be evaluated. Based on literature references (Sheehan, 1983; Ware, 1993; Leon et al, 1992), the SDS and SF-36 have po-

tential merits but little documentary evidence that demonstrates their value and actual performance for the intended purpose. One major limitation of cross-sectional measures such as the SDS and SF-36 is that they cannot gain unbiased quantitative information on daily life contexts and activities (Barge-Schaapveld et al, 1995). Hence, a time-based method to measure disability can mirror the not-directly-observable extent to which an individual is interested in and capable of engaging in his/her subjective experiences in his/her natural setting. Timebased measures, ie, by collecting self-reports from subjects immediately after repeated random signals, appear to be feasible (Barge-Schaapveld et al, 1995), and their application in psychiatric patients in parallel with other scales may capture entities the investigators want to measure but are diffused or obscured. CONCLUSIONS The measurement of disability with the SDS and SF-36 in groups of subjects with anxiety disorders may be obsolete. There is the need for more specific and simple instruments based on a general consensus concerning disability definition in this patient population. REFERENCES American Psychiatric Association. Diagnostic and Statistical Manual qfMental Disorders. 4th ed. Washington DC: American Psychiatric Association, 1994 Barge-Schaapveld DQCM, Nicolson NA, Gerritsen Van Der Hoop R, DeVries MW. Changes in daily life experience associated with clinical improvement in depression. J Affective Disorders 1995;34:139-54 Bodlund O, Kullgren C, Ekselius L, Lindstr6m E, von Knorring L. Axis V - Global Assessment of Functioning Scale. Evaluation of a self-report version. Acta Psychiatr Stand 1994;90:342-7 Cronbach LJ. Coefficient alpha and the internal s~ucture of tests. Psychometrika 1951; 16:297-334 Curran VH. Memory functions, alertness and mood of long-term benzodiazepine users: a preliminary investigation of the effects of a normal daily dose. J Psychophamuwol 1992:6:69-75 Davidson JRT, Ports N, Richichi E, Krishnan R et al. Treatment of social phobia with clonazepam and placebo, J Clin Psychopharmacol 1993;13:423-8 Feinstein AR, Josephy BR, Wells CK. Scientific and clinical problems in indexes of functional disability. Ann Intern Medicine 1986; 105:413-20 Hamilton M. The assessment of anxiety states by rating. Br J Med Psychol 1959:32:50-5 Golotnbok S, Moodley P, Lader M. Cognitive impairment in longterm benzodiazepine users. Psychol Med 1988; 18:365-74 Keller MB, Lavori PW, Friedman B, Nielsen E et al. The Longitudinal Interval Follow-Up Evaluation: a comprehensive method for assessing outcome in prospective longitudinal studies. Arch Cen Psychiatr3, 1987;44:540-8 Leon AC, Shear KM, Portera L, Klerman LC. Assessing impairment

Measuring disability in subjects with anxiety disorder in patients with panic disorder: the Sheehan Disability Scale. Soc Psychiatry Psychiatr Epidemiol 1992;27:78-82 Leon AC, Portera L, Weissman MM. The social costs of anxiety disorders. Br J Psychiatry 1995; 166 (27s):19-22 Markowitz JS, Weissman MM, Ouellette R, Lish JD, Klerman CL. Quality of life in panic disorder. Arch Cen Psychiatry 1989;46: 984-92 Massion AO, Warshaw MC, Keller MB. Quality of life and psychiatric morbidity in panic disorder and generalized anxiety disorder. Am J Psychiatry 1993;150:600-7 Myers JK. Yale Greater New Haven Health Survey. New Haven: Yale University, 1980 Sheehan DV. The arL~:iet)'disease. New York: Scribner, 1983 Spector WD. Functional disability scales. In: Spilker B, ed. Qualio"

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of life and pharmacoeconomics in clinical trials. Philadelphia/New York: Lippincott-Raven, 1996;133-43 Testa MA, Simonson DC. Assessment of quality-of-life outcomes. N Engl J Med 1996;334:835-40 Ware JE Jr. SF - 36 health survey manual and interpretation guide. Boston: The Health Institute (New England Medical Center), 1993 Warshaw MG, Fierman E, Pratt L, Hunt Met al. Quality of life and dissociation in anxiety disorder patients with histories of trauma or PTSD. Am J Psychiatry 1993;150:1512-16 Weissman M, Bothwell S. Assessment of social adjustment by patient self-report. Arch Cen Ps~'~hiatr3' 1976;33:1111-15 World Health Organization. International classification of impairments, disabilities, and handicaps. World Health Organization, Geneva, 1980