S. Onstad

High interrater reliability for the structured clinical interview for DSM-III-R axis I (SCID-I)

The interrater reliability of the Structured Clinical Interview for DSM‐III‐R (SCID) was studied. Fifty‐four audiotaped SCID interviews were rated independently by 3 raters. The highest interrater agreements were observed for schizophrenia (0.94), major depressive disorder (0.93), dysthymia (0.88), generalized anxiety disorder (0.95), panic disorder (0.88), alcohol use disorder (0.96) and other psychoactive substance use disorder (0.85). The remaining diagnoses of mood and anxiety disorders obtained acceptable interrater agreement (0.70–0.80), with an exception for obsessive‐compulsive disorder (0.40). The poorest agreement was obtained for somatoform disorders (– 0.03). Lack of hierarchy in DSM‐III‐R allows for multiple Axis I diagnoses. Interrater reliability for multiple diagnoses was tested. Agreement was generally good for combinations of 2 diagnoses, and poorer when 3 diagnoses were combined. Our findings confirm that SCID yields highly reliable diagnoses. SCID is recommended for research on mental disorders.

A twin study of DSM-III-R anxiety disorders

The prevalence of anxiety disorders was studied in a sample of 20 monozygotic (MZ) and 29 dizygotic (DZ) co‐twins of anxiety disorder probands. A comparison group of co‐twins of 12 MZ and 20 DZ twin probands with other non‐psychotic mental disorders was also studied. All subjects were personally interviewed with the Structured Clinical Interview for DSM‐III‐R Axis I (SCID‐I). Panic disorder was significantly more prevalent in co‐twins of panic probands. Generalized anxiety disorder (GAD) was more prevalent in co‐twins of GAD probands with a history of mood disorder (NS). Post‐traumatic stress disorder was significantly more prevalent in co‐twins of anxiety probands and was more prevalent in MZ than in DZ co‐twins. The prevalences of social and simple phobia were equal in co‐twins of anxiety and comparison probands. For both panic disorder and generalized anxiety disorder the MZ:DZ concordance ratio was more than 2:1. The results support the hypothesis of a genetic contribution in the etiology of panic disorder, generalized anxiety disorder and post‐traumatic stress disorder. The hypothesis that simple and social phobia are mainly caused by environmental experiences was also supported.

Twin concordance for DSM-III-R schizophrenia

The monozygotic (MZ)/dizygotic (DZ) concordance rates for schizophrenia and the relationship between schizophrenia and schizophrenic spectrum disorders were studied in a sample of 31 MZ and 28 DZ schizophrenic probands and their co‐twins. All subjects were personally interviewed with structured diagnostic instruments and classified according to DSM‐III‐R criteria. The concordance rates of 48% for MZ twins and 4% for DZ twins indicate a genetic transmission of DSM‐III‐R schizophrenia. In addition to the schizophrenic co‐twins, 3 MZ co‐twins had a nonaffective psychotic disorder, thus supporting the hypothesis that genes are involved in the development of Axis I schizophrenic spectrum disorders. Schizotypal and paranoid personality disorders were observed in both MZ and DZ co‐twins. These disorders may be familially related to schizophrenia, but a genetic relationship was not confirmed for the Axis II spectrum disorders. A substantial number of MZ co‐twins of schizophrenic probands had no mental disorder.

Schizotypal personality disorder inside and outside the schizophrenic spectrum.

The concept of schizotypal personality disorder has been heavily discussed since its introduction into the official classification of mental disorders in DSM-III. The aim of this study was to investigate the difference between schizotypal personality disorder within and outside the genetic spectrum of schizophrenia. Schizotypals with and without schizophrenic cotwins and first-degree relatives were compared, with individuals with other mental disorders and no mental disorders as controls. It appeared that only inadequate rapport and odd communication were more pronounced among schizotypals within, compared to schizotypals outside the schizophrenic spectrum. Schizotypals outside the schizophrenic spectrum, however, scored higher than schizotypals inside the schizophrenic spectrum on ideas of reference, suspiciousness, paranoia, social anxiety, self-damaging acts, chronic anger, free-floating anxiety and sensitivity to rejection. Interestingly, the four last features are seldom observed among schizotypals inside the schizophrenic spectrum. Monozygotic non-schizophrenic cotwins of schizophrenics score high on inadequate rapport, odd communication, social isolation and delusions/hallucinations. Monozygotic non-schizophrenic cotwins of schizotypals outside the schizophrenic genetic spectrum score high on illusions, depersonalization, derealization and magical thinking. Negative schizotypal features appear to be inside the schizophrenic spectrum, while positive borderline-like features are outside having another genetic endowment.

Mental disorders in first-degree relatives of schizophrenics

A total 215 first‐degree relatives of 88 twin probands with schizophrenia, mood disorders and nonaffective psychoses were studied. The twins’ parents and siblings were personally interviewed with structured diagnostic instruments and diagnosed in accordance with DSM‐III‐R criteria. The first‐degree relatives were interviewed by interviewers who were blind to the twins’ diagnoses. Schizophrenia and schizotypal personality disorder were significantly more frequent in first‐degree relatives of schizophrenic twins. Respectively, anxiety and mood disorders were significantly more prevalent among the parents and siblings of probands with mood disorders. Schizophrenic spectrum disorders were significantly more common in the families of schizophrenic probands compared with relatives of mood disorder probands, thus confirming a relationship between schizophrenia and schizophrenic spectrum disorders. However, we cannot, based on our study, specify whether this relationship is caused by genetic or environmental factors.

The heritability of common phobic fear: a twin study of a clinical sample.

The aim of this study was to investigate the genetic and environmental contribution to common phobic fears, and to relate the findings to contemporary theories about the etiology of common phobic fears. Self-reported common phobic fear was studied in a treatment sample of 23 monozygotic and 38 same-sex dizygotic twin pairs. Heritability of .47 was observed for common phobic fear of small animals and social fear, and a heritability of .30 in common agoraphobic fear. For common fear of nature phenomena and situational fear, the heritability was 0. The finding that common nature and situational fears were solely caused by environmental factors is in support of learning theory, whereas results for animal, social, and other common phobic fear are in support of an integrative theory of biological preparedness, learning history, and a cognitive style of fearful expectation.

A family study of anxiety disorders: familial transmission and relationship to mood disorder and psychoactive substance use disorder

The prevalence of mental disorders in 76 first‐degree relatives (parents and nontwin siblings) of 33 subjects with anxiety disorder was compared with the prevalence of mental disorders in 45 first‐degree relatives of 20 subjects with mood disorder and 13 first‐degree relatives of 6 subjects with psychoactive substance use disorder. All subjects were personally interviewed with the Structured Clinical Interview for DSM‐III‐R Axis I (SCID I). Interrater reliability was high for most diagnoses. Significantly more first‐degree relatives of subjects with anxiety disorder had panic disorder and generalized anxiety disorder compared with relatives of probands with mood disorder. Significantly more female than male relatives of anxiety subjects suffered from anxiety disorders; there were no gender differences in the prevalence of anxiety disorders in relatives of mood and psychoactive substance use disorder (PSUD) subjects. The combination of anxiety and mood disorder was overrepresented in first‐degree relatives of subjects with the same type of comorbidity. In relatives of subjects with mixed anxiety and psychoactive substance use disorder, but no mood disorder, there was an overrepresentation of PSUD; mainly alcohol abuse or dependence.

Family interaction: parental representation in schizophrenic patients

12 monozygotic (MZ) and 19 same‐sexed dizygotic (DZ) twin pairs discordant for DSM‐III‐R schizophrenia completed the Parental Bonding Instrument (PBI). The schizophrenic twins described their parents as less caring and being more overprotective compared to their non‐schizophrenic co‐twins. These results were independent of age, sex and zygosity. Difference in paternal overprotection was the most important variable discriminating between the schizophrenic probands and their co‐twins. Three different hypotheses regarding these findings are discussed.

Birthweight and obstetric complications in schizophrenic twins.

Birthweight and obstetric complications were registered retrospectively in 24 monozygotic (MZ) twin pairs. Sixteen pairs were discordant and 8 pairs were concordant for DSM‐III‐R schizophrenia. There was no significant intrapair difference in birthweight between the 2 groups of MZ twins. Prematurity was more often observed in the discordant pairs, but neither differences in prematurity nor differences in obstetric complications between the concordant and discordant twins reached significance. No difference in respect of family history of schizophrenia between the 2 groups of MZ twins was found. In the discordant pairs, no significant difference between the schizophrenic twin and the nonschizophrenic co‐twin was observed regarding birth order, birthweight or physical condition at birth.

Parental representation in twins discordant for schizophrenia

Parental representation was assessed with the Parental Bonding Instrument (PBI) in 12 monozygotic (MZ) and 19 dizygotic (DZ) same-sexed twin pairs discordant for DSM-III-R schizophrenia. The schizophrenic twins reported less care and more overprotection from both parents than the non-schizophrenic co-twins. Multiple regression analysis disclosed that the results were independent of sex and age. Furthermore, the analysis demonstrated that whether the twins were monozygotic or dizygotic had no impact on the results. A stepwise discriminant analysis showed that difference in perceived paternal protection was the most important variable distinguishing between schizophrenic probands and their non-schizophrenic co-twins.