A family study of sex differences in the diagnosis of atypical schizophrenia

Reduced fertility in schizophrenia: here to stay?

Studies of reproduction among individuals with schizophrenia published in this century are reviewed. Past studies suggesting normalization of reproductive deficits are disputed in view of recent reports of a persistent impairment. The handicap appears to be more significant among men with schizophrenia. The implications of these findings for genetic research in schizophrenia are discussed.

Fertility in schizophrenia: results from a contemporary US cohort

To investigate procreation in schizophrenia, as well as gender-related differences, female patients with schizophrenia (n = 79, DSM-III-R criteria) were compared with screened female controls (n = 124) and subsequently with male patients (n = 86). Two outcomes were investigated: (i) the proportion of subjects with one or more children (an index of fertility) and (ii) the number of children per subject among those with one or more children (an index of fecundity). Multivariate analysis was used to control for confounding variables. No significant differences in fertility between female patients and controls were detected, but reduced fecundity was noted among female patients past the reproductive period. Male patients showed a significant reduction in both fertility and fecundity compared to female patients. These results suggest that there is a relatively small impairment of fecundity among female patients compared with controls, but that there are more significant gender-related differences in both fertility and fecundity. The latter have important implications for the genetics of schizophrenia.

The impact of gender and age at onset on the familial aggregation of schizophrenia

Some recent family studies have shown that the familial risk for schizophrenia is higher in female than in male schizophrenics. It is debated whether the risks for the other disorders, such as schizotypal personality disorder or affective disorders in families of schizophrenics are similarly influenced by the proband's gender. Also, the reason for the effect of proband's gender on the recurrence risk for schizophrenia has not been clarified. This family study (159 probands, 589 first degree relatives) confirms that schizophrenia, but also schizophrenia spectrum disorders were more frequent in families of female compared with male schizophrenics. Neither age at onset in probands nor the interaction between gender and age at onset in probands had a relevant impact on the risk figures in relatives. Affective disorders occurred in families independently of the probands' gender. Aetiological heterogeneity or ascertainment bias may account for the modifying effect of proband's gender 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.

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.

How does gender influence age at first hospitalization for schizophrenia? A transnational case register study

Numerous studies have reported a lower mean age at first hospitalization for schizophrenia in males than in females. For this finding not only a gender difference in age at first onset of schizophrenia, but also other factors can be responsible. With the aim of providing a comprehensive analysis of gender differences in onset, symptomatology and course of schizophrenia, we started by testing the hypothesis postulating a gender difference in mean age at first hospitalization. By using the Danish and the Mannheim psychiatric case registers we analysed all hospital admissions for schizophrenia and related diagnoses and all previous admissions for other diagnoses of the Danish population in 1976 and those of the inhabitants of the German city of Mannheim in the period of 1978-80. Artefacts were controlled for systematically. The impact of intervening variables such as selection factors as well as the influence of gender on the ascription of a diagnosis of schizophrenia for the first time were assessed. We found a mean difference of 5 to 6 years in age at first hospitalization between males and females in both countries when a broad definition of the diagnosis was used and of 4 to 5 years when a restrictive definition was applied. The higher mean age at first hospitalization among females is not attributable to artefacts, diagnostic procedures or to any essential extent to gender differences in help-seeking behaviour or occupational status. When a distinction was made between 'single' and 'married', the significant difference in age at first hospitalization between the sexes disappeared in singles. With case register data and without knowing the chronological order of marriage and onset of the disease, it remains an open question whether this finding can be explained by purely correlative associations between sex, marital status and age of onset or by causal effects.