Abstract

This chapter characterises the age of onset (AOO) of schizophrenia spectrum disorders and summarises findings regarding a range of clinical and social outcomes, cognition, brain structure and mortality. The peak AOO for schizophrenia spectrum disorders is between 20 and 29 years, during which the estimated incidence among males and females was 4.15 and 1.71 per 10,000 person-years, respectively. Male gender has been linked with earlier onset age, although corresponding gender differences do not exist among those with family history and cannabis use. Early-onset schizophrenia has been linked with, for example, higher familial risk, poor premorbid social adjustment and cannabis use. In adult samples, earlier AOO was associated with worse outcome regarding hospitalisations, negative symptoms, relapses, social and occupational functioning, and global outcome. Earlier onset has also been linked with more severe outcomes in childhood and adolescence schizophrenia. In addition, early AOO has been linked with larger cognitive deficits and brain alterations. In the few existing studies, later AOO has been linked with a higher suicide rate. In all, the current study found a number of differences between patients with a different AOO. However, the studies on AOO are relative heterogeneous in methodology and have provided varying results. More good-quality studies are needed that include patients without restriction on the onset age. AOO is an important characteristic of schizophrenia that could help when examining the origin, genetic mechanism and care of schizophrenia. Understanding factors that influence AOO in schizophrenia may offer clues to aid prevention of or delaying the onset of this debilitating group of disorders.