Occurrence and clinical correlates of psychiatric co-morbidity in delusional disorder

Eur Psychiatry 2001 ; 16 : 222-8 © 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S0924933801005685/FLA

ORIGINAL ARTICLE

Occurrence and clinical correlates of psychiatric comorbidity in delusional disorder G. Maina*, U. Albert, A. Badà, F. Bogetto Department of Neuroscience, Psychiatric Unit, University of Turin, Via Cherasco 11, 10126 Turin, Italy (Received 15 June 2000; revised 16 February 2001; accepted 26 February 2001)

Summary – The present study investigated the occurrence and the clinical correlates of psychiatric co-morbidity in a sample of 64 patients with delusional disorder (DD). Subjects were evaluated with a semi-structured interview for the collection of demographic and clinical features of the disorder; co-morbid axis 1 disorders were determined according to the clinical interview using DSM-IV by Othmer and Othmer. Delusional disorder subjects with and without co-morbid diagnoses were compared to investigate whether the presence of another psychiatric disorder influenced the clinical features of the illness. Seventy-two percent of the subjects had at least one additional lifetime psychiatric diagnosis. High lifetime co-morbidity was found with affective disorders, whose onset generally had been subsequent to the onset of DD. Patients with at least one co-morbid disorder (N = 46) had an earlier age at onset, presented for the first psychiatric consultation at an earlier age, and were younger at index evaluation for this study with respect to patients without co-morbidity (N = 18). Types of DD differed significantly according to the presence/absence of lifetime co-morbid disorders: DD patients with co-morbidity were in most cases persecutory type (54.4%) while DD patients without co-morbidity were mixed type (66.7%). Our data indicate that there is a considerable proportion of patients whose DDr is strictly connected with other co-occurring psychiatric disorders (mainly affective disorders), which exert an influence on the phenomenology of the illness. © 2001 Éditions scientifiques et médicales Elsevier SAS clinical features / co-morbidity / delusional disorder

INTRODUCTION In clinical samples of patients with psychotic disorders, co-morbidity appears to be a relevant phenomenon. In a sample of hospitalized patients with current psychotic symptoms, Cassano et al. [2] found a lifetime prevalence of psychiatric co-morbidity of 58.1% in subjects with a diagnosis of nonaffective psychosis (schizophrenia, schizophreniform disorder, schizoaffective disorder, and delusional disorder). However, within the

*Correspondence and reprints.

group of nonaffective psychosis patients, analyses of axis I co-morbidities were carried out without discriminating between patients with different diagnoses. According to another study performed by Strakowski et al. [18], 40.2% of subjects at first hospitalization for an acute psychotic episode present at least one axis I co-morbid disorder. With regard to nonaffective psychoses, the proportion of subjects having additional diagnoses was higher. Fifty percent of patients admitted to the hospital because of a schizophrenic spectrum

Psychiatric co-morbidity in delusional disorder

disorder (schizophrenia, schizophreniform disorder, or schizoaffective disorder) and 50% of those admitted because of an atypical psychosis (brief reactive psychosis and psychosis NOS) had at least one other major psychiatric disorder; this percentage decreased to 11.1% for subjects with delusional disorder (DD). However, the small size of the DD sample (N = 9) prevents us from generalizing these results. Analysis of the nonaffective group revealed that the patients with psychiatric co-morbidity were younger, had longer hospitalizations, and were less likely to have been married [18]. In a study whose aim was to analyze mood disturbances occurring within a delusional disorder, Marino et al. [10] reported a considerable prevalence of mood disturbances (50.7%). In particular, a high proportion (35.2%) of delusional patients were affected by a recurrent form of mood disturbance. Prevalence rates of psychiatric co-morbidities appear to be considerably higher in epidemiologic samples drawn from the general population: 93% of subjects with nonaffective psychosis received at least one additional psychiatric diagnosis in the National Comorbidity Survey study. In particular, 73.4% of subjects with nonaffective psychosis were found to have at least an additional lifetime diagnosis of mood disorder, 71.4% of anxiety disorder, and 58.5% of substance use disorder [9]. Epidemiologic studies focused on DD patients are still missing, due to the low prevalence of the disorder in the general population. Although co-morbidity between axis I psychiatric disorders and schizophrenic spectrum disorders appears to be a relevant phenomenon [2, 9, 10, 18], none of the studies that have been performed specifically evaluated the prevalence and pattern of syndrome co-morbidity in DD patients. Given then the scarcity of data on DD patients, the aims of the present descriptive study were to examine the occurrence of DSM-IV axis I disorders in a clinical sample of patients given a principal diagnosis of DD and to investigate whether the presence of a current or lifetime co-morbid disorder could influence the clinical features of the DD. MATERIAL AND METHODS Subjects Subjects were recruited from outpatients consecutively referred to the Department of Neuroscience, Psychiatric Unit, of the University of Turin (Italy) over a period Eur Psychiatry 2001 ; 16 : 222–8

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of 2 years. To be admitted to the study, all patients had to meet DSM-IV and ICD-10 criteria for a principal diagnosis of DD. The clinical investigation for DSM-IV diagnoses was developed according to Othmer and Othmer (14, 15). As there is a significant difference in duration of the delusions between DSM-IV and ICD-10 criteria (l month vs 3 months), diagnoses were also applied according to the ICD-10 criteria. Moreover, DD diagnosis was confirmed by two different investigators prior to study entry. In addition, patients had to have a minimum rating of 18 on the Brown Assessment of Beliefs Scale (BABS) and a minimum rating of 4 on the first item of this scale, as suggested by the authors that validated the scale [3]. The BABS is a seven-item clinician-administered semi-structured scale designated to assess delusionality of beliefs in a broad range of psychiatric disorders, with good psychometric properties, including inter-rater reliability, test-retest reliability, and internal consistency. Subjects had to be at least 18 years of age and willing to voluntarily participate in the study. Subjects gave their informed consent after the procedure was fully explained. Exclusion criteria were the presence of a mental retardation. Interviews Data were obtained through the administration of a semi-structured interview with a format that covered the following areas: demographic data: gender, index age, marital status, and years of education; principal and co-morbid diagnoses were performed by a semistructured examination protocol according to DSM-IV criteria for diagnoses of current psychiatric disorders and longitudinal disorders. Only axis I diagnoses were considered and the clinical investigation for DSM-IV diagnoses was developed according to Othmer and Othmer [14, 15]. In cases of DD co-morbidity, intake evaluators also rated the onset of the diagnosed disorders on the basis of the patient’s historical report during the assessment. The ‘primary’ disorder was that which occurred chronologically before all other disorders; and clinical features of DD: age at onset, age at first psychiatric consultation, delusional themes and type of DD according to DSM-IV: erotomanic, grandiose, jealous, persecutory, somatic, mixed or unspecified. In addition, the following rating scales were administered to each patient: the Brown Assessment of Beliefs Scale (BABS) [3]; the Social Adaptation Self-Evaluation Scale (SASS) [1]; the Hamilton Rating scale for Anxiety

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(HAM-A) [5]; and the 17-item Hamilton Rating Scale for Depression (HAM-D) [6].

Table I. Demographic and clinical features of 64 patients with delusional disorder. Characteristic

Interviewers and raters The inclusion diagnosis was made by two senior psychiatrists (F.B. and G.M.) who were not directly involved in the study. The semi-structured interviews were conducted in person by two trained psychiatrists (U.A. and A.B.) with significant clinical and research experience in psychiatry, including extensive experience in conducting clinical research interviews. Statistical analysis Frequencies of axis I diagnoses were calculated: co-morbid diagnoses included concomitant and lifetime occurrence of an axis I disorder according to DSM-IV criteria. For the purpose of the study, all DD subjects were divided into two groups according to the presence or absence of at least one lifetime co-morbid diagnosis: the two resulting groups, DD with and without co-morbid diagnoses, were compared to investigate whether the presence of another psychiatric disorder influenced the clinical features of the DD. Our study was designed to provide descriptive information; therefore, primarily descriptive statistics were used to analyze data. Between-group comparisons of categorical variables were made with the Pearson’s χ2 test. Continuous variables were compared by using Student’s t-test for two-class comparisons. RESULTS Seventy-one subjects with DD were screened consecutively for the inclusion in the study: seven (9.9%) refused to participate and 64 (90. 1%) completed the evaluation and thus constitute our sample. Demographic and clinical characteristics of the investigated sample are summarized in table I. Co-morbidity Twenty (31.3%) patients had at least one actual co-morbid axis I diagnosis and 46 (71.9%) at least one lifetime psychiatric diagnosis; only 18 (28. 1%) patients with DD had never suffered from another mental disorder in their lives. Table II shows co-morbid diag-

Gender Males Females Marital status Single Married Widowed Separted/divorced Education (years) Age at onset of the DD Age at first psychiatric consultation Actual age (index age) Rating scales BABS SASS Ham-D HAM-A

N

% SD

22 42

34.4 65.6

27 28 3 6 11.0 37.9

42.2 43.8 4.7 9.3 ± 3.9 ± 10.5

44.2

± 13.5

47.9

± 13.9

20.2 34.2 12.1 12.6

± 1.8 ± 8.6 ± 4.4 ± 6.1

BABS: Brown Assessment of Beliefs Scale; SASS: Social Adaptation of Self-Evaluation Scale; HAM-D: Hamilton Rating Scale for Depression; HAM-A: Hamilton Rating Scale for Anxiety.

noses, both in an intra-episodic and in a longitudinal perspective. Concerning the time sequence of DD and co-morbid diagnoses, in most cases mood disorders appeared to be secondary to DD (64.7%: see table III). When co-morbid, anxiety disorders appeared to be primary: almost all cases of co-morbidity in our sample had had the onset of the anxiety disorder prior to the onset of the DD (table III). Comparison of DD with and without co-morbidity DD with and without co-morbidity did not show statistically significant differences in sex distribution, marital status, and level of education (years of education)(table IV). As shown in table IV, patients with at least one co-morbid disorder (N = 46) had an earlier age at onset of the disorder, presented for the first psychiatric consultation at an earlier age, and were younger at index evaluation for this study with respect to patients without co-morbidity (N = 18). Eur Psychiatry 2001 ; 16 : 222–8

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Psychiatric co-morbidity in delusional disorder Table II. Actual and lifetime co-morbidities in 64 patients with delusional disorder. Diagnosis At least one co-morbid disorder Mood disorders Major depression Dysthymia Depressive disorder NOS At least one Anxiety disorders OCD Specific phobia Social phobia GAD At least one Other disorders Eating disorders Hypochondriasis Substance use disorder Delirium

Actual

Lifetime

N

%

N

%

20

31.3

46

71.9

9 4 1 14

14.1 6.3 1.6 21.9

23 7 4 34

35.9 10.9 6.3 53.1

0 2 0 0 2

– 3.1 – – 3.1

6 3 2 2 11

9.4 4.7 3.1 3.1 17.2

3 1 0 0

4.7 1.6 – –

5 4 3 1

7.8 6.3 4.7 1.6

NOS: not otherwise specified; OCD: obsessive-compulsive disorder; GAD: generalized anxiety disorder.

No differences were found between the two groups concerning the type of onset and the rating scale scores (except for the HAM-D score, being higher in subjects with co-morbid disorders). The type of delusional disorder most frequently encountered (identified according to the main delusional themes as described in DSM-IV) was the perse-

cutory type (40.6%), followed by the mixed (29.7%), somatic (14.1%), jealous (10.9%). and unspecified types (4.7%). No cases of the erotomanic or grandiose types were found. As shown in table V, types of DD differed significantly according to the presence/absence of lifetime co-morbid disorders: DD patients with co-morbidity were in most cases the persecutory type

Table III. Lifetime co-morbid diagnoses of 64 patients with delusional disorder (DD) whose primary co-morbid disorder preceded the DD. Co-morbid diagnosis is primary Diagnosis

N

N

%

At least one co-morbid disorder

46

22

47.8

23 7 4 34

8 4 0 12

34.8 57.1 0 35.3

6 3 2 2 11

6 2 2 2 10

100 66.7 100 100 90.9

5 4 3 1

3 4 3 0

60.0 100 100 0

Mood disorders Major depression Dysthymia Depressive disorder NOS At least one Anxiety disorders OCD Specific phobia Social phobia GAD At least one Other disorders Eating disorder NOS Hypochondriasis Substance use disorder Delirium

NOS: not otherwise specified; OCD: obsessive-compulsive disorder; GAD: generalized anxiety disorder. Eur Psychiatry 2001 ; 16 : 222–8

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Table IV. Comparison between patients with (N = 46) and without (N = 18) psychiatric lifetime co-morbid disorders: demographic and clinical features. Characteristic

DD with

DD without

t or χ2 (df = 1)

P

co-morbidity N (%) Gender Males Females Marital status Single Married Widowed Separated/divorced Education (years) Age at onset of DD Age at first consultation Actual age (index age) Rating scales BABS SASS HAM-D HAM-A

N (%) 1.126

.289

4.311 (df = 3)

.230

14 (30.4%) 32 (69.6%)

8 (44.4%) 10 (55.6%)

20 (43.5%) 22 (47.8%) 1 (2.2%) 3 (6.5%) 11.4 (± 3.6) 35.4 (± 10.5) 40.9 (± 12.3) 43.4 (± 12.2)

7 (38.9%) 6 (33.3%) 2 (11.1%) 3 (17.7%) 10.0 (± 4.7) 44.2 (± 7.6) 52.6 (± 13.3) 59.4 (± 11.0)

1.272 –3.229 –3.339 –4.841

.208 .002 .001 < .001

19.9 (± 1.8) 34.5 (± 9.2) 12.9 (± 4.0) 13.5 (± 5.7)

20.8 (± 1.8) 33.6 (± 6.9) 9.9 (± 4.8) 10.4 (± 6.6)

–1.674 .385 2.567 1.832

.099 .701 0.13 .072

BABS: Brown Assessment of Beliefs Scale; SASS: Social Adaptation of Self-Evaluation Scale; HAM-D: Hamilton Rating Scale for Depression; HAM-A: Hamilton Rating Scale for Anxiety.

(54.4%) while DD patients without co-morbidity were mixed type (66.7%). DISCUSSION This is the first study that, to the best of our knowledge, specifically investigated the occurrence and clinical correlates of psychiatric co-morbidity in a sample of patients with DD. Another strength is that all patients were recruited from the same site.

Table V. Comparison between patients with (N = 46) and without (N = 18) psychiatric lifetime co-morbid disorders: type of delusional disorder according to DSM-IV. DD with DD without χ2 (df = 4) co-morbidity N (%) N (%) Type of DD Erotomania 0 0 Grandiose 0 0 Jealous 3 (6.5%) 4 (22.1%) Persecutory 25 (54.4%) 1 (5.6%) Somatic 8 (17.4%) 1 (5.6%) Mixed 7 (15.2%) 12 (66.7%) Unspecific 3 (6.5%) 0

24.496

P

< .001

Demographic and clinical characteristics of our sample are generally consistent with those of previous reports [7, 8, 13, 17, 19]: our findings confirm that DD is predominant in females, is equally distributed in singles and married subjects, has an onset in the late thirties/early forties, and that there is a consistent delay between the onset of the disorder and the first psychiatric consultation. Concerning the type of DD, Yamada et al. [19] found that the most frequently encountered type in their sample was the persecutory type, followed by the somatic type, jealous type and unspecified type. Our findings are consistent with their report except for the fact that we found a considerable proportion of subjects (30%) having delusions characteristic of more than one of the types identified by DSM-IV but without a predominant theme (mixed type). Our results are also consistent with Hsiao’s et al. [7] report of a higher frequency of persecutory delusions followed by mixed type, jealous, somatic and unspecified types. Comparisons with other DD patient samples are difficult because most reports in the literature focused their interest on a specific delusional theme, mainly on erotomanic patients [4, 16] or monodelusional hypochondriasis [11, 12]. Eur Psychiatry 2001 ; 16 : 222–8

Psychiatric co-morbidity in delusional disorder

Psychiatric co-morbidity was common in our group of DD patients: 71.9% of subjects had at least one additional lifetime psychiatric diagnosis. Our results suggest that co-morbidity is a relevant phenomenon in DD as it is in other disorders within the schizophrenic spectrum [2, 9, 18]. With regard to DD patients, Strakowski et al. [18] found a lifetime co-morbidity rate of 11% in a subsample of nine patients, significantly lower than the co-morbidity rate we found in the present study. However, the small size of their sample, the higher proportion of males (56% in their sample versus 34% in ours), and differences in inclusion criteria and interview procedures make it difficult to compare our results with their findings. Moreover, our result of a higher co-morbidity rate may be due, at least in part, to the DSM-IV diagnostic system, which encourages multiple diagnoses. Mood disorders were the mental disorders most frequently found in lifetime co-morbidity with DD (53.1%), followed by anxiety disorders (17.2%). The high prevalence of mood disorders found in our sample is consistent with other studies: Marino et al. [10] reported a 50.7% prevalence of mood disturbances in their DD sample, and a high proportion (35.2%) of delusional patients affected by a recurrent form of mood disturbance; in about 42% of these patients the onset of the mood disturbance preceded the onset of the delusional disorder by a considerable interval of time. It is noteworthy that in our sample 35% of patients with a lifetime co-morbidity with mood disorders had the onset of the mood disturbance prior to the onset of the DD. Hisao et al. [7] reported that 43% of their patients had depressive symptoms at their first visit. With regard to the temporal relationship of axis I disorders that occur together with DD, mood disorders appear to be in most cases subsequent to the onset of the DD, while in almost all cases anxiety disorders preceded the onset of the DD. This confirms that DD, although generally less impairing in the interpersonal and occupational roles of patients than other schizophrenic spectrum disorders, is associated with mood disorder in a considerable proportion of patients. Such a high rate of co-morbidity and the influence of a co-occurring affective disorder on the main delusional symptomatology need to be further investigated and clarified in order to provide clinicians with a useful therapeutic approach. Anxiety disorders appear to be less frequently associated with DD, and anxiety symptoms usually precede the onset of delusions. It is noteEur Psychiatry 2001 ; 16 : 222–8

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worthy that our sample comprised six subjects with OCD that subsequently lost insight into the nature of their obsessions and compulsions and progressively developed a delusional disorder whose main delusional theme was unrelated to the primary obsessivecompulsive symptomatology. According to our results, co-morbidity exerts an influence more on the onset than on the clinical presentation of the disorder: psychiatric co-morbidity was associated with earlier ages at onset of the DD, with earlier ages at first visit to a psychiatrist and with earlier ages at index evaluation. Different interpretations of these results are offered, and probably all of them have contributed to our results: 1) patients with ‘pure’ delusional disorder presented later to the psychiatrist due to the characteristic lack of insight into this disorder, while patients with co-morbid disorders presented earlier for other co-morbid symptoms, and thus were diagnosed prior to ‘pure’ DD patients; and 2) the presence of a co-morbid disorder made an individual more vulnerable to the development of another disorder, in that case to the onset of the delusional disorder. Considering symptomatological features, psychiatric co-morbidity was associated with a greater proportion of persecutory types (54.4% vs 5.6%), and fewer mixed types (15.2% vs 66.7%). No differences in symptom severity and in functional impairment were found between the two subgroups. CONCLUSION Our data indicate that there is a considerable proportion of patients whose DD is strictly connected with other co-occurring psychiatric disorders (mainly affective disorders), which exert an influence on the phenomenology of the DD. Our results need to be replicated in larger clinical and/or epidemiological samples from the general population. REFERENCES 1 Bosc M, Dubinj A, Polin V. Development and validation of a social functioning scale, the Social Adaptation Self-Evaluation Scale. Eur Neuropsychopharmacol 1997 ; 7 (Suppl 1) : S57S70. 2 Cassano GB, Pini S, Saettoni M, Rucci P, Dell’Osso L. Occurrence and clinical correlates of psychiatric comorbidity in patients with psychotic disorders. J Clin Psychiatry 1998 ; 59 : 60-8. 3 Eisen JL, Phillips KA, Baer L, Beer DA, Atala KD, Rasmussen SA. The Brown Assessment of Beliefs Scale: reliability and validity. Am J Psychiatry 1998 ; 155 : 102-8.

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