Aetiological heterogeneity of schizophrenia: the problem and the evidence

Schizophrenia spectrum and other psychotic disorders

Since its earliest conceptualization, schizophrenia has been considered a disorder of "young men." Contemporary research suggests that there are sex differences in schizophrenia that are both transdiagnostic and representative of general sex/gender differences across the psychopathology spectrum. This chapter selectively summarizes representative sex/gender differences in clinical expression, epidemiology, risk factors, treatment, as well as course and outcome in schizophrenia. The consistent sex differences found, such as onset age, generic brain anomalies, and hormonal involvement, are not specific to schizophrenia or necessarily to psychopathology. It is suggested that in working with those diagnosed as meeting the current criteria for schizophrenia, clinicians adopt a transdiagnostic framework informed by sex and gender role processes.

Structural brain imaging in schizophrenia

The subtle pathomorphology of schizophrenia is gradually being unraveled through the application of increasingly sophisticated brain imaging techniques. There is now compelling evidence of subtle brain abnormalities in patients with schizophrenia. It less clear, however, whether these reflect a widespread cortical involvement, or more selective involvement among interconnected neural systems, or more focal pathology. The extent of brain changes, their etiopathologic significance, and putative clinical correlates are reviewed in this article.

Lack of gender differences in familial schizophrenia

Objective:Gender appears to have a significant impact on the prevalence, age at onset, symptoms and outcome of schizophrenia. This study examines gender effects in a population of familial schizophrenic patients in Ireland.

Method:Families with two or more siblings suffering from schizophrenia, as defined by DSM-III-R were ascertained in Ireland. The final sample comprised 169 siblings from 80 families. Siblings were interviewed using the Structured Clinical Interview for DSM-III-R (SCID), the Scale for the Assessment of Negative Symptoms (SANS) and the Strauss-Carpenter Levels of Functioning Scale. The difference between males and females for various clinical features were calculated.

Result:There was a marked excess of affected males (65% male and 35% female). When the excess of male subjects was taken into account there was no significant excess of same-sex as compared to opposite-sex pairs. There were no significant difference between males and females for age at onset, age at first admission, symptoms or level of outcome.

Conclusion:The excess of males and the lack of gender differences for clinical features found in this study may, in part, be due to the narrow diagnostic criteria used. Alternatively, at least some of these findings may be specific to this Irish sample. Further research is a need to see if these findings can be replicated in other countries.

Specific P300 features in patients with cycloid psychosis

In previous studies, low amplitudes and asymmetrical topography with right-sided peaks of the P300-evoked response have been repeatedly described in schizophrenic patients. A sample consisting of 18 patients with cycloid psychosis fulfilling the criteria of Perris and Brockington and 18 controls was investigated with a standard auditory odd-ball paradigm and multichannel evoked potential recordings. Patients had normal P300 topographies and latencies but significantly higher amplitudes than the controls. Higher than normal P300 amplitudes have not been described in any other psychiatric disorder until now, and indicate an enhanced level of arousal. Future studies are expected to shed light on the question of whether high P300 amplitudes are transitory sequelae of the acute psychotic episode or a trait of cycloid psychosis.

Specific P300 features in patients with cycloid psychosis

In previous studies, low amplitudes and asymmetrical topography with right-sided peaks of the P300-evoked response have been repeatedly described in schizophrenic patients. A total of 18 patients with cycloid psychosis fulfilling the criteria of Perris and Brockington and 18 controls were investigated with a standard auditory odd-ball paradigm and multichannel-evoked potential recordings. Patients had normal P300 topographies and latencies but significantly higher amplitudes than controls. Higher than normal P300 amplitudes have not been described in any other psychiatric disorder until now, and indicate an enhanced level of arousal. Future studies are expected to shed light on the question of whether high P300 amplitudes are transitory sequelae of the acute psychotic episode or a trait of cycloid psychosis.

Genetic heterogeneity in catatonic schizophrenia: a family study

In family study concentrating on 139 probands with chronic DSM-III-R schizophrenia, catatonic type, 83 probands (41 women, 42 men) met the criteria for periodic catatonia and 56 probands (14 women, 42 men) for systematic catatonia according to the Leonhard classification. The reliability and stability of this subclassification were tested by 2 experienced psychiatrists working independently of each other. Both diagnosticians were kept blind as to the probands' family history. The 139 probands had a total of 543 first-degree relatives. Only those hospitalized for schizophrenia were allocated to the group of afflicted family members. Diagnostic reliability was kappa statistic 0.93 and diagnostic stability during catamnesis reached 97% and kappa of 0.93. Life-table analyses revealed that the age-corrected risks were significantly different in periodic and systematic catatonia. In systematic catatonia mothers had a risk of 6.8%, fathers 2%, and randomly selected sibs 3%. IN periodic catatonia an excess of homologous psychoses was apparent: There was a risk of 33.7% for mothers, 15.4% for fathers, and 24.4% for sibs. The quota of afflicted parents (33 of 161) was higher than that of sibs (26 of 162). In periodic catatonia, 59% of the families were multiple afflicted with pronounced unilineal vertical transmission. In 10% of the families 3 successive generations suffered from the disease and were treated in hospital. The results of the study led to the following hypotheses: Periodic and systematic catatonia are valid subgroups of DSM-III-R schizophrenia. In systematic catatonia heritability is very low. Periodic catatonia is a familial disorder. Homogeneity of familial psychoses and unilineal vertical transmission with anticipation are consistent with a major gene effect. Periodic catatonia seems to be a promising candidate for molecular genetic evaluation.

Electrical brain activity in schizophrenia described by equivalent dipoles of FFT-data

Since results of conventional FFT-power-analysis are reference-dependent, only unambiguous neurophysiological data should be used for a functional physiological interpretation of EEG-data. FFT-approximation with successive center-of-gravity-dipole calculation gives unambiguous EEG-data with regard to recording reference. In the present investigation 22 medicated schizophrenic patients were compared with 22 healthy age- and sex-matched controls with regard to spontaneous resting EEG. More anterior and superficial equivalent-dipoles were found in the beta-bands for schizophrenic patients compared to healthy control subjects. There was a tendency of increased beta-activity in schizophrenic subjects. With more severe schizophrenic symptoms (higher BPRS-score), the more anterior was the equivalent-dipole localization in the beta 1-band, and the deeper in the theta-band. The different locations of the beta-band dipoles in schizophrenic patients suggest that different neuronal populations generate beta-activity in schizophrenia compared to healthy controls. FFT-approximation allows a substantial and meaningful data reduction in multichannel recordings and will hopefully help in understanding pathological brain functions in schizophrenia.

Differences in P300 amplitudes and topography between cycloid psychosis and schizophrenia in Leonhard's classification

In a polydiagnostic approach, we investigated the parameters of auditory P300 in a group of 18 remitted schizophrenics and in 18 age- and sex-matched controls. All patients fulfilled the criteria of schizophrenic disorder according to DSM-III-R. Applying Leonhard's classification, patients were to be subdivided into 7 cycloid psychosis and 11 Leonhard's schizophrenics. Patients with cycloid psychosis fulfilled the operational criteria of Brockington et al. We found significantly lower P300 amplitudes in the group of Leonhard's schizophrenics than in controls and in cycloid psychosis, whereas no difference could be shown between patients with cycloid psychosis and controls. Both the maxima and the minima of the P300 field map were dislocated significantly to the right in the group of Leonhard's schizophrenics but not in cycloid psychosis.