Schizotypy and genetic loading for schizophrenia impact upon neuropsychological status in bipolar II and unipolar major depressive disorders

Abstract Background Growing evidence suggests that schizotypy and genetic loading for schizophrenia both represent risk for the development of schizophrenia. Although these conditions are known to be associated with neurocognitive impairments, such an association has not been studied in patients with bipolar II disorder (BPII) or unipolar major depressive disorder (UP). Methods Forty-one depressed patients with BPII, 131 patients with UP and demographically matched 225 healthy controls were recruited. Schizotypy was assessed by the Schizotypal Personality Questionnaire. Neuropsychological functioning was measured by the Wechsler Memory Scale-Revised, the Wechsler Adult Intelligence Scale-Revised and the Wisconsin Card Sorting Test. Results Mood disorder patients performed significantly worse than controls in verbal and visual memory, working memory and processing speed. BPII patients performed significantly more poorly than UP patients in verbal memory and executive functioning. Both BPII and UP patients demonstrated significantly greater schizotypal traits than controls. Schizotypy was significantly negatively correlated with verbal comprehension both in BPII and UP patients and with working memory and processing speed in healthy controls. Patients who had one or more first-degree relatives with schizophrenia performed significantly more poorly than the remaining patients in all cognitive domains. Limitations Most of our patients were on psychotropic medication, and the sample of BPII patients was not very large. Conclusions Liability for schizophrenia could play a pivotal role in neurocognitive functioning in mood disorders, suggesting that such liability might lie on a continuum ranging from normality through mood disorders to full-blown schizophrenia.