A Longitudinal Study of Premorbid IQ Score and Risk of Developing Schizophrenia,Bipolar Disorder, Severe Depression, and Other Nonaffective Psychoses

Abstract

There is strong evidence that patients with schizophrenia show impairmentsin a wide variety of neuropsychological tasks, including attention, executivefunction, language, memory, and general intellectual ability.¹ Thus,when investigating risk factors for schizophrenia, case-control studies ofpremorbid cognitive ability may be particularly biased if this is assessedafter onset of the disorder. Overall results from such studies for schizophreniaindicate that impairment in intellectual ability may exist from early in lifeand is not just a consequence of the pathological process of disease onset.²