Gender and schizophrenia: implications for understanding the heterogeneity of the illness

Subject selection biases in clinical trials: data from a multicenter schizophrenia treatment study

To evaluate subject selection biases in clinical trials, demographic characteristics (gender, race, and age) of subjects at different phases of evaluation for a multicenter maintenance trial in schizophrenia were examined. Six thousand twelve diagnostically appropriate subjects were screened for the study; of these, 1,320 met eligibility criteria and 528 (9% of the screened sample) entered the study. Women, blacks, and older subjects were more likely not to meet eligibility criteria; women and older subjects were more likely and blacks were less likely to refuse study participation. Overall, compared with the screened population, the sample of subjects who entered the study contained proportionately fewer women (33 vs. 43%), more blacks (48.5 vs. 41%), and fewer older subjects (mean age of the entered sample was 29.4 +/- 7.4 vs. 34.8 +/- 11.3 years for the screened population). Having identified these selection factors, a second goal was to assess the potential clinical relevance of selection biases of these magnitudes on clinical trials using models of hypothetical studies with different degrees of selection bias. These showed that selection biases would rarely change overall study outcomes to a clinically relevant degree. However, in our models, selection biases did limit the ability to make inferences about results for select small subgroups of the study population. Investigators should consider collecting data on the recruitment process to allow estimation of the effects of selection biases on the generalizability of their findings.

Information processing, social skill, and gender in schizophrenia

The relationships among information processing, social skill, and gender in individuals with chronic schizophrenia were investigated. Although there were no gender differences in information processing, social skill, or negative symptoms, performance on information-processing tasks was related to various indices of social skill (e.g., paralinguistic skill) for female, but not male, inpatients. This pattern of results remained after statistical controls were applied for age, illness chronicity, and positive symptoms.

Genetic heterogeneity may in part explain sex differences in the familial risk for schizophrenia

The purpose of this study was to attempt, in part, to explain significant sex differences in the familial risk (FMR) for schizophrenia found in previous studies. We hypothesized that, like probands, relatives of male vs. female probands may express different forms or subsyndromal symptoms of schizophrenia, i.e., differential expression of flat affect. Studied were 332 schizophrenic probands defined by Diagnostic and Statistical Manual of Mental Disorders, 3rd ed. (DSM-III), criteria and 725 first-degree relatives from well-known retrospective cohort family studies. Results showed that relatives of male probands were at significantly higher risk for expressing flat affect than relatives of female probands, which did not hold for relatives of normal controls. Logistic regression was used to show that when flat affect was incorporated into the definition of affected among relatives, sex differences in FMR disappeared.

Correlates of left-handedness in a large sample of schizophrenic patients

Questionnaire data concerning hand preference from the parents of 686 schizophrenic patients were used to test predictions relevant to neurodevelopmental models of schizophrenia. In line with predictions, left-handed patients (n = 94) had a more frequent history of difficult birth, more childhood cognitive and behavioural abnormalities and more persistent auditory hallucinations than did right-handed patients.

Psychotic states arising in late life (late paraphrenia). The role of risk factors

BACKGROUND

This study explored the association between 'late paraphrenia' and various risk factors such as female gender, sensory impairment, marital status, positive family history of psychoses, and the presence of abnormal neurological signs. It was hypothesised that patients would show significantly more abnormal neurological signs than controls.

METHOD

Inclusion criteria for the diagnosis of late paraphrenia were fulfilled by 47 patients, including in-patients, out-patients, day-patients, and those living in the community. Thirty-three age-, sex-, education-, and premorbid IQ-matched elderly controls were recruited from luncheon clubs in Southwark and Lambeth (London, UK). A scale for the assessment of neurological soft and hard signs was developed for this study. The Abnormal Involuntary Movement Scale (AIMS) and the Tardive Dyskinesia Rating Scale (TDRS) were also used.

RESULTS

There was a high female-to-male ratio (42:5), and a fourfold increase in the risk of patients having hearing impairment (odds ratio = 4.15, Clodds = 1.36 to 12.63). There was no difference between the two groups in visual difficulties nor in marital status. Patients were approximately ten times more likely to be living on their own (odds ratio = 10.61; Clodds = 3.59 to 31.33) and 16 times more likely to be considered socially isolated (odds ratio = 16.65; Clodds = 5.39 to 51.40). There was no difference between patients and controls in frequency of schizophrenia-like family history. Patients were more likely than controls to exhibit neurological soft signs (z = 4.70; P < 0.001; Cld = 4.61 to 9.63). The presence of abnormal involuntary and tardive dyskinesia movements was associated with the use of antipsychotic medication.

CONCLUSION

Women appear to run a greater risk of developing late paraphrenia, especially those who are socially isolated and present with associated hearing impairment. The increased presence of neurological soft signs among patients indicates that brain disease may be a critical factor in the development of psychotic symptoms in late life.

HLA-DR types in Japanese schizophrenics: analysis by group-specific PCR amplification

An association of HLA-DR8 and DR1 with DSM-III schizophrenia has been reported in Japan (Miyanaga et al. (1984) Biol. Psychiatr. 19, 121-129). To further investigate this preliminary finding, we compared HLA-DR types in 44 unrelated Japanese schizophrenics (DSM-III-R) with those in 51 unrelated, healthy Japanese volunteers. Group-specific PCR amplification was used in the determination of HLA-DR in the patients. No significant difference was observed in the frequency of any DR types between patients and controls, after statistical correction for multiple testing. However, the frequency of DR1 in our patients (23%) and controls (10%) was almost the same as those in the previous report (22% vs. 10%), which means that there is a suggestive trend which could become significant if numbers were larger. It is argued that an exact determination of HLA-DR by DNA typing is important in current HLA studies of schizophrenia.

Are schizophrenia and affective disorder related?: the problem of schizoaffective disorder and the discrimination of the psychoses by signs and symptoms

Schizophrenia and affective disorder are separately classified. Schizoaffective disorder has been considered a variant of these, or representing several diseases. Some hypothesize a psychosis continuum. One test of these contrasting views involves discriminating the psychoses by their classic symptoms. We used discriminant function analyses to assess the ability of systematically recorded psychopathology to distinguish 167 DSM-III schizophrenics from 74 affectives. We divided the schizophrenics into chronic and schizoaffective subgroups. We discriminated chronic schizophrenics from affectives, but schizoaffectives overlapped both groups. Schizoaffective/unipolars were like chronic schizophrenics, and schizoaffective/bipolars were like affectives. However, these discriminations also substantially overlapped, and among non-affective positive features formal thought disorder was best at discrimination. Our findings do not fully support the present classification system, and suggest that its emphasis on hallucinations and delusions is overvalued.

Age at onset, sex, and familial psychiatric morbidity in schizophrenia. Camberwell Collaborative Psychosis Study

BACKGROUND

Although a genetic component in schizophrenia is well established, it is likely that the contribution of genetic factors is not constant for all cases. Several recent studies have found that the relatives of female or early onset schizophrenic patients have an increased risk of schizophrenia, compared to relatives of male or late onset cases. These hypotheses are tested in the current study.

METHOD

A family study design was employed; the probands were 195 patients with functional psychosis admitted to three south London hospitals, diagnosed using Research Diagnostic Criteria (RDC), and assessed using the Present State Examination (PSE). Information on their relatives was obtained by personal interview of the mother of the proband, and from medical records. Psychiatric diagnoses were made using Family History-Research Diagnostic Criteria (FH-RDC), blind to proband information.

RESULTS

There was a tendency for homotypia in the form of psychosis within families. The lifetime risk of schizophrenia in the first degree relatives of schizophrenic probands, and the risk of bipolar disorder in the first degree relatives of bipolar probands, were 5-10 times higher than reported population risks. Relatives of female and early onset (< 22 years) schizophrenic probands had higher risk of schizophrenia than relatives of male and late onset schizophrenic probands. However, this effect was compensated in part by an excess of non-schizophrenic psychoses in the relatives of male probands.

CONCLUSIONS

These results suggest a high familial, possibly genetic, loading in female and early onset schizophrenia, but do not resolve the question of heterogeneity within schizophrenia.

Sustained attention and positive formal thought disorder in schizophrenia

Deficits in sustained attention and formal thought disorder (FTD) are two characteristics of schizophrenia that might be expressions of a common pathology. This study examined whether a measure of enduring (post-treatment, stabilized) deficits in sustained attention, the Continuous Performance Test (CPT) could predict FTD. In addition, a comparison was made of CPT performance between subjects with schizophrenia (n = 41) and healthy controls (n = 28). Results replicated previous findings of significantly poorer performance by individuals with schizophrenia compared to normal controls. Within the schizophrenia group, significant correlations were found between FTD and CPT measures. In order to assess predictability of FTD, a hierarchical multiple regression analysis was used. CPT errors and gender both significantly predicted FTD. The most robust prediction was of residual FTD (post-treatment, stabilized) by CPT commission errors. These results lend support to the proposition that a subsyndrome within schizophrenia exists that is characterized by deficits in sustained attention and positive formal thought disorder. Furthermore, this subsyndrome might be more common in males than females.

A reconsideration of the relationship between cerebral structural abnormalities and family history of schizophrenia

In a study of 229 schizophrenic patients for whom reliable family history information was available, ventricular size and incidence of ventricular enlargement were found to be greater in male cases without a family history of schizophrenia. A significant sex by family history interaction on cerebral ventricular dimension was detected. The age-corrected morbid risk for schizophrenia was lower among first degree relatives of male probands with ventricular enlargement vs. those with normal ventricles, but similar in relatives of females with and without ventricular enlargement. On the other hand, no association was found between family history and degree of cortical atrophy. A meta-analysis of published studies on the issue revealed 20% larger ventricles in patients without any known genetic predisposition for schizophrenia.

Schizophrenia: sex and familial morbidity

Several recent studies have found a greater risk of schizophrenia among the relatives of female schizophrenic probands than the relatives of male schizophrenic probands. These results are contradictory to those of earlier studies. The current investigation, using family data collected in the 1950's and 1960's in Sweden, did not find a difference in the risk of schizophrenia among the relatives of male and female schizophrenic probands. However, significantly more relatives of female probands than relatives of male probands had manic-depressive psychosis. These findings suggest that the earlier studies may have included some female schizophrenic probands who would be classified as having manic-depression by modern criteria.

Gender differences in age at onset of schizophrenia

Numerous studies have found that male schizophrenic patients have earlier ages at onset than females. However, none of these studies have corrected the observed ages for known gender differences in the age distribution of the population. Using a pre-existing data set, we applied a non-parametric method to correct the male and female distributions of observed age at onset for sex-specific age distributions. The distributions of observed age at onset indicated earlier onset among males. After correction, the age-at-onset distributions shifted toward older ages, but the difference between males and females remained statistically significant. Thus, gender differences in the age at onset of schizophrenia are not artefactual.

The subtyping of schizophrenia in men and women: a latent class analysis

Latent class analysis on an epidemiologically based series of 447 first contact patients with a broad diagnosis of schizophrenia revealed evidence for two subtypes: a 'neurodevelopmental' type characterized by early onset, poor pre-morbid social adjustment, restricted affect and a male:female ratio of 7:3; and a 'paranoid' type characterized by later onset, persecutory delusions and an almost equal sex ratio. A third 'schizoaffective' subtype, whose existence was less clear cut, was almost entirely confined to females and characterized by dysphoria and persecutory delusions, and had negligible familial risk of schizophrenia. The aetiological, biological and clinical significance of this typology remains to be tested.

Extended latent class approach to the study of familial/sporadic forms of a disease: its application to the study of the heterogeneity of schizophrenia

When no method exists for detecting genetic forms of a disorder, epidemiologists classify probands according to the presence or absence of an affected relative (familial or sporadic). Not only is this a surrogate measure but if the risk for the disorder is associated with characteristics such as age and gender, then probands with varied distributions of these characteristics among their relatives are subject to misclassification. A latent class approach is presented which explicitly models the relationship between the affected status of the relatives and the unobservable familial/sporadic status of the proband in order to adjust for these characteristics. Lastly, an approach is introduced to correct for attenuation in measures of association between familial/sporadic status and other variables that could result if probands are misclassified. This approach incorporates the latent class probabilities directly into the regression model without classifying probands. These methods are applied to a study of the heterogeneity of schizophrenia.

Sex differences in schizophrenia: a demographic, symptomatic, life history and genetic study

Twenty-one male and 32 female inpatients who met the criteria of schizophrenia according to the Research Diagnostic Criteria were compared for demographic, symptomatic, life history, and genetic variables. Female schizophrenics were marginally less likely to have auditory hallucinations; They were more likely to have early loss experiences (either bereavement or separation from a parent) before the age of 16. No other differences were found between the men and women.

Gender and mortality in schizophrenia: do women act like men?

The effect of gender on mortality was explored for a sample of DSM-III diagnosed schizophrenics followed for up to 42 years. The data for 332 cases and 304 matched normal controls were from the retrospective cohort family studies, the Iowa 500 and non-500. Survival analysis and Cox regression models were used to test the effects of gender, illness status and their interaction on the risks for natural and unnatural deaths. The control men experienced significantly more unnatural deaths than the control women, which was not found for schizophrenic men and women. The unnatural death rate among schizophrenic women was similar to the rate for schizophrenic and control men, and significantly higher than for control women during the early phase of the illness. Findings suggest that some factors that predict suicide may be similar for schizophrenic women and men.

Sex and schizophrenia: effects of diagnostic stringency, and associations with and premorbid variables

In a case-record study, all first-contact patients with non-affective functional psychosis from a defined area over 20 years were diagnosed according to operational criteria of varying stringency and emphasis, and incidence rates for each set of criteria determined by sex and age at onset; data on premorbid adjustment were also analysed by sex and age at onset. The overall first-contact incidence of non-affective functional psychosis was approximately equal in men and women; however, the ratio of male to female incidence rates rose progressively when RDC (1.2), DSM-III-R (1.3), DSM-III (2.2), and Feighner (2.5) criteria for schizophrenia were applied. Schizophrenia was most common in young males and least common in older males, with females occupying an intermediate position. Schizophrenia in young males, particularly when stringently defined, was especially likely to be associated with single status, poor work and social adjustment, and premorbid personality disorder. The results suggest that schizophrenia syndrome is heterogeneous, and young males are especially prone to a severe neurodevelopmental form of illness associated with premorbid deficits.

Estimating age at onset distributions: the bias from prevalent cases and its impact on risk estimation

Since many disorders have a variable age at onset, knowing the age at onset distribution of a disease facilitates epidemiologic analyses in several ways. The age at onset distribution is commonly used to estimate morbidity risks or the recurrence risks in genetic counseling. Unfortunately, estimation of a disease's age at onset distribution is not straightforward. The observed age at onset distribution obtained from prevalent cases is usually used in these epidemiologic analyses. Through simulation studies, we show that, in certain situations, the observed age at onset distribution has a non-negligible downward bias. This bias can lead to a substantial underestimation of the morbidity risk or the recurrence risk. The simulations also demonstrate that a non-parametric approach for correcting the age at onset distribution works well even when mortality increases after onset. The results have implications for diseases that have adult onset and/or increased mortality after onset. We suggest that researchers should use corrected age at onset distributions, rather than relying on observed distributions, in the calculation of either morbidity risks or recurrence risks.

Sex and schizophrenia: vive la différence

Epidemiological research in schizophrenia is back in fashion and has taken an iconoclastic turn. Received truths about schizophrenia had a reassuring stability about them, rather like Euclidean geometry. In contrast to, and perhaps in reaction to, the frustrating nebulousness of the disorder itself, its distribution had the attributes of a universal constant: incidence and symptoms unchanging over time and across space–and between the sexes. Dissenting voices were few, but now are growing in number and volume. One sex difference, that of age at onset of schizophrenia, has been accepted since Kraepelin's time, although is still unexplained. But sex differences in incidence, course, and symptoms are now being mooted which hint at sex-dependent differences in aetiology. Much of the re-examination of this issue has sprung from the work of Jill Goldstein and colleagues at Harvard, Robin Murray, David Castle, and colleagues at the Institute of Psychiatry, as well as others, such as Mathias Angermeyer in Mannheim.

Gender differences in the clinical expression of schizophrenia

Gender differences have been reported for a variety of clinical measures in patients with schizophrenia. Clinical characterization may be helpful in identifying symptom clusters which can then be linked to underlying brain function. In this study 74 men and 33 women meeting DSM-IIIR criteria for schizophrenia were studied off medication and rated on measures of symptom type and severity, as well as premorbid and current function. Men were more severely impaired in ratings of negative symptoms, while positive symptoms were not significantly different. There were also differences in premorbid and current functioning, with women manifesting better social functioning than men.

Gender and the familial risk for schizophrenia. Disentangling confounding factors

Recent studies of the effect of gender on the familial risk for schizophrenia have shown that relatives of females have a higher risk for schizophrenia than relatives of males. This study attempts to explain the effect by examining factors found to differentiate schizophrenic men and women and found to be related to the familial risk for schizophrenia. Cox proportional hazard regression model was used to examine the simultaneous effects of age at onset, season of birth, and premorbid history, controlled for symptoms that have been found to differ by gender (dysphoria, paranoia, and flat affect). Results showed that the effect of gender on the transmission of schizophrenia could not be explained by gender differences in age at onset, symptom expression, premorbid history, and winter birth. However, premorbid history had an effect on familial risk independent of gender, indicating that probands with a poor premorbid history had a lower familial risk for schizophrenia than those with a good premorbid history. Implications of the findings are discussed.

Contribution of family, cognitive and clinical dimensions to long-term outcome in schizophrenia

A multivariate approach incorporating both biological and psychosocial factors was used in a cross-sectional study of schizophrenic inpatients and outpatients selected to represent opposite ends of the outcome spectrum. Twenty-six RDC-diagnosed chronic schizophrenic patients hospitalized continuously for 18 months or longer, and 26 patients with a history of at least three years of community tenure without rehospitalization were matched for sex, age, ethnicity, SES and chronicity, and assessed on a structured family interview (Social Behavior Assessment Schedule), neuropsychological test battery, Brief Psychiatric Rating Scale and Premorbid Asociality Scale. Stepwise discriminant function analysis was performed; family ratings of patients' problem behaviors was the most powerful discriminator between the two groups and a composite measure of neuropsychological functioning ranked second. Other significant discriminators were BPRS scores, availability of social support to the family and age of onset. Family ratings of patient behavior were related to ratings of family burden and to BPRS scores. Further research is needed to understand the complex interactions between the diverse sets of social, clinical and neurobiological factors that determine long-term outcome in schizophrenia.

Schizophrenia: gender and familial risk

The morbid risks for schizophrenia and any nonaffective psychosis in the first degree relatives of male and female schizophrenic probands were compared utilizing Cox proportional hazards models. The schizophrenic probands (275 male; 106 female) were drawn from a larger sample of hospitalized patients obtained by systematically screening all psychiatric admissions to 15 facilities over a six-year period. Proband diagnoses (DSM-III) were based on a direct assessment of the patient and a review of medical records. The family history method was used to obtain information about the first degree relatives of the probands. Cox proportional hazards models were adjusted for duration of illness of the proband and gender of the relatives. First degree relatives of female probands had significantly higher morbid risks for schizophrenia and nonaffective psychosis than relatives of male probands. The differential risk for schizophrenia in the relatives of male and female probands demonstrated in this study, as well as others, suggests that males and females may be at different risk for subtypes of the disorder.

Gender differences in the incidence of definite schizophrenia and atypical psychosis--focus on negative symptoms of schizophrenia

In a catchment area study of 101 first inceptions of schizophrenia, mania and atypical psychoses, women were significantly more likely to have atypical psychosis and men were more likely to have definite schizophrenia. Negative symptoms such as affective flattening and poverty of speech were already present in many cases, and were significantly increased in patients with definite schizophrenia (geometric mean 5.6) compared with those with atypical psychosis (geometric mean 3.2) and mania (geometric mean 1.5). Negative symptoms were also twice as severe in men (geometric mean 5.5) than women (geometric mean 2.6). There was a significant increase in negative symptom severity with longer illness and greater depression, but the diagnosis and the sex effects were not caused by these factors. We suggest that our findings are further support for the hypothesis that men have a greater biological vulnerability to negative symptoms and consequent social disability in the face of psychosis, particularly a schizophrenic psychosis, and that this may be one explanation for the apparently greater risk of definite schizophrenia and its poorer prognosis in men.

Low birth weight and a family history of schizophrenia predict poor premorbid functioning in psychosis

Risk factors thought to predispose to schizophrenia, and premorbid functioning, were assessed blind to diagnosis by interviewing the mothers of 73 patients with DSM-III schizophrenia or affective psychosis. Higher risk of schizophrenia in relatives, lower mean birth weight, a more frequent history of obstetric complications, and poorer educational achievement distinguished the patients with schizophrenia from those with affective psychosis. Low birth weight and obstetric complications each predicted childhood schizoid and schizotypal traits. Poor social adjustment between ages 5 and 11 was predicted by low birthweight and by a family history of schizophrenia.

Estimating effects of proband characteristics on familial risk: II. The association between age at onset and familial risk in the Maryland schizophrenia sample

In this report we apply methods outlined in the companion paper [Liang, Genet Epidemiol 8:329-338, 1991] to study the association between proband age at onset and familial risk among first-degree relatives of 374 schizophrenic probands. The analyses take into consideration the potential problems of censoring and correlation of age at onset within families. All analyses were done by gender of the proband; age at onset was dichotomized. The results of the analyses of the male probands suggest that there is an increased risk of schizophrenia among the relatives of male probands who have an onset prior to age 17 when compared to relatives of male probands who have an onset later than 16. We did not find an association between age at onset and familial risk among the female probands, but this may be due to the smaller number of female probands and the lower power associated with the analyses.

Schizophrenia: age at onset, gender and familial risk

In a family history study of 366 schizophrenic probands and their 1851 first-degree relatives, we found a relationship between age at onset of psychosis in the male probands and the risk for schizophrenia in their relatives. The relatives of male schizophrenic probands whose onset of psychosis occurred when they were younger than 17 years of age had an increased risk of schizophrenia when compared with the relatives of male probands with an age at onset greater than 17. We did not find an association between age at onset of psychosis in the female probands and familial risk. Cox proportional hazards models permitted us to examine the relationship between age at onset of psychosis in the probands and familial risk while controlling for possible confounding effects.

Gender and short-term outcome in schizophrenia

227 first-contact schizophrenic patients (DSM-III) were followed-up for 2 years. The psychiatric teams responsible for the treatment of the patients conducted a detailed, standardized interview with the patients at entry and during the follow-up. Men showed a poorer premorbid heterosexual development and they also tended to be more withdrawn than women. Following the onset of the illness, men still failed to establish satisfactory heterosexual relationships, they suffered more often from negative symptoms, and they displayed poorer working capacity and functional ability than women. At the beginning of the follow-up men had a more pessimistic view of the development of their life situation over the next 2 years, a prediction which turned out to be correct. The predictions made by the psychiatric teams were very similar. In their plans for treatment the psychiatric teams recommended primarily psychotherapeutic methods for female patients--and women actually went to psychotherapy more often than men--whereas it was felt that the rehabilitation of men should concentrate on working capacity and basic social skills. The poorer psychosocial outcome of men seems to be due to their poor premorbid development--specifically heterosexual development--and negative symptoms. Together, these factors form a particularly harmful combination from the point of view of the social role of men in our society. The treatment system seems to be unable to adequately respond to the specific needs of men suffering from schizophrenia.

Sex differences in the familial transmission of schizophrenia

The hypothesis that schizophrenic men have a lower familial risk for schizophrenia than schizophrenic women was tested using the DSM-III-diagnosed samples of the Iowa 500 and non-500 family studies. Survival analyses were used to test for differences in the risk for schizophrenia and spectrum disorders, for sex of proband and sex of relative, controlled for fertility effects and ascertainment bias. Male and female relatives of schizophrenic men had a significantly lower risk for schizophrenia, schizophreniform, and schizoaffective disorders than relatives of schizophrenic women. However, the effect was not significant for the full spectrum nor when analysed by sex of relative. Sex differences in the risk for other psychiatric disorders among relatives of schizophrenic probands were not significant.