Assessment of cognition in non-affected full biological siblings of patients with schizophrenia

Schizophrenia is a devastating psychotic illness which is like the most mental disorders, shows complex inheritance; the transmission of the disorder most likely involves several genes and environmental factors. It is difficult to judge whether a particular person without schizophrenia has predisposing factors for the said disease. A few studies have shown the relative sensitivity and reliability of cognitive and psychophysiological markers of brain function as the susceptibility factors for schizophrenia which may aid us to find people with an increased risk of complex disorders like schizophrenia. The present work is an exploration on cognitive impairments in unaffected siblings of patients suffering from schizophrenia with a framework to explore why a mental disorder occurs in some families but not in others.

This is a single point non-invasive study of non-affected full biological siblings of patients with schizophrenia, involving administration of a battery of neuropsychological tests to assess the cognitive function in the sibling group and a control group of volunteers with no history of psychiatric illness. The control group was matched for age, gender, and education. The siblings were also divided on the basis of the type of schizophrenia their siblings (index probands) were suffering from and their results compared with each other.

The siblings performed significantly poorly as compared to the controls on Wisconsin card sorting test (WCST), continuous performance test (CPT), and spatial working memory test (SWMT). The comparison between the sibling subgroups based on the type of schizophrenia in the index probands did not reveal any significant difference.

These findings suggest that there is a global impairment in the cognition of the non-affected siblings of patients of schizophrenia. Cognitive impairment might be one of the factors which will help us to hit upon people who are predisposed to develop schizophrenia in the future.