A recent study has suggested that the brain-expressed genes for G72 and D-amino-acid oxidase (DAAO) exert an influence on susceptibility to schizophrenia. Our aim was to replicate this finding in German schizophrenic patients and to assess whether G72 and DAAO might also contribute to the development of bipolar affective disorder. We genotyped seven single-nucleotide polymorphisms (SNPs) in the G72 gene and three in the DAAO gene in 599 patients (299 schizophrenic, 300 bipolar) and 300 controls. At G72, individual SNPs and a four-marker haplotype were associated with schizophrenia. The most significant SNP as well as the haplotype were also associated with bipolar affective disorder (BPAD). DAAO was associated with schizophrenia, but not with BPAD. The association of variation at G72 with schizophrenia as well as BPAD provides molecular support for the hypothesis that these two major psychiatric disorders share some of their etiologic background.

We have investigated the gene for dystrobrevin-binding protein 1 (DTNBP1), or dysbindin, which has been strongly suggested as a positional candidate gene for schizophrenia, in three samples of subjects with schizophrenia and unaffected control subjects of German (418 cases, 285 controls), Polish (294 cases, 113 controls), and Swedish (142 cases, 272 controls) descent. We analyzed five single-nucleotide polymorphisms (P1635, P1325, P1320, P1757, and P1578) and identified significant evidence of association in the Swedish sample but not in those from Germany or Poland. The results in the Swedish sample became even more significant after a separate analysis of those cases with a positive family history of schizophrenia, in whom the five-marker haplotype A-C-A-T-T showed a P value of.00009 (3.1% in controls, 17.8% in cases; OR 6.75; P=.00153 after Bonferroni correction). Our results suggest that genetic variation in the dysbindin gene is particularly involved in the development of schizophrenia in cases with a familial loading of the disease. This would also explain the difficulty of replicating this association in consecutively ascertained case-control samples, which usually comprise only a small proportion of subjects with a family history of disease.

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These data suggest that bipolar affective disorder with persecutory delusions constitutes a distinct subgroup of bipolar affective disorder that overlaps with schizophrenia.

Demographical and clinical characteristics have been reported to modulate the risk for suicide. This study analysed demographical and clinical characteristics with respect to lifetime suicide attempts in 500 individuals affected with schizophrenic or affective disorders. Suicide attempts were associated with poor premorbid social adjustment, low age at onset, low scores on the "Global Assessment Scale" and childlessness in females.