Initially termed “dementia praecox,” schizophrenia was first described by the German psychiatrist Emil Kraepelin in the late 19th century. Kraepelin distinguished dementia praecox from manic depressive illness, primarily a mood disorder, on the basis of differences in course and outcome: schizophrenia was observed to have a chronic and deteriorating course with a poor outcome, while manic depression was seen to have a cyclic “relapsing-remitting” course, with a more favourable long-term outcome. The name schizophrenia (literally “split mind”) was coined in the early 20th century by the Swiss psychiatrist Eugen Bleuler, and much later manic depression was renamed bipolar disorder. However, problems in the distinctions between these two conditions were soon identified and noted by Kraepelin himself in his later writings. Considerable overlap was seen in clinical features, course, and outcome. The more recent diagnostic category of schizoaffective disorder may be seen to encompass composite forms of mood and schizophrenic disorders. Schizophrenia is now more commonly regarded as a clinical syndrome rather than a single disease entity; there is significant heterogeneity in clinical expression, and considerable overlap of both clinical and biological features with other psychiatric conditions. Scientific efforts are yet to delineate the causes and pathophysiology of schizophrenia, although some significant advances in understanding the neurobiology and treatment mechanisms have been made in the past 50 years.
A strong genetic basis for schizophrenia is indicated by family and molecular genetic studies. However, a clear role for environmental influences in the development of schizophrenia is also well established. Current molecular genetic studies of schizophrenia encompassing worldwide consortia have been able to account for an increasing but minor fraction of risk for schizophrenia in common genetic loci. Rare genetic variations, such as copy number deletions and duplications, are also emerging as important risk indicators. High overlap in the heritability of bipolar and schizoaffective disorder within families has also been shown in large-scale epidemiological research.
In terms of impact and incidence, schizophrenia ranks among the top 10 causes of disability in developed countries and incidence is estimated at 15.2/100 000, with current prevalence estimated at 4.6/1000 (McGrath et al., 2008).