There is significant and independent variation of incidence of schizophrenia and other psychoses in terms of sex, age, ethnicity, and place. This confirms that environmental effects at the individual, and perhaps neighborhood level, may interact together and with genetic factors in the etiology of psychosis.

Background. The incidence of schizophrenia in the African-Caribbean population in England is reported to be raised. We sought to clarify whether (a) the rates of other psychotic disorders are increased, (b) whether psychosis is increased in other ethnic minority groups, and (c) whether particular age or gender groups are especially at risk.

Patients with schizophrenia and related psychoses have an excess of minor neurological abnormalities (neurological soft signs) of unclear neuropathological origin. These include poor motor coordination, sensory perceptual difficulties and difficulties in sequencing complex motor tasks. Neurological soft signs seem not to reflect primary tract or nuclear pathology. It still has to be established whether neurological soft signs result from specific or diffuse brain structural abnormalities. Studying their anatomical correlates can provide not only a better understanding of the aetiopathogenesis of soft signs, but also of the pathophysiology of schizophrenia. Surprisingly few studies have investigated the brain correlates of neurological soft signs. In the present study, we investigated the relationship between brain structure and neurological soft signs in an epidemiologically based sample of 77 first-episode psychosis patients. We used the Neurological Evaluation Scale for neurological assessment and high-resolution MRI and voxel-based methods of image analysis to investigate brain structure. Higher rates of soft neurological signs (both motor and sensory) were associated with a reduction of grey matter volume of subcortical structures (putamen, globus pallidus and thalamus). Signs of sensory integration deficits were additionally associated with volume reduction in the cerebral cortex, including the precentral, superior and middle temporal, and lingual gyri. Neurological soft signs and their associated brain changes were independent of antipsychotic exposure. We conclude that neurological soft signs are associated with regional grey matter volume changes and that they may represent a clinical sign of the perturbed cortical-subcortical connectivity that putatively underlies psychotic disorders.

A multitide of factors play a role in the aetiology of schizophrenia. Comparison of environmental factors in these groups may identify factors that contribute to the aetiology of schizophrenia.