Schizoaffective disorder: from Kraepelin to genes.

The original term schizoaffective disorder was invented 75 years ago by Kasanin as a response to diagnostic difficulty with patients who did not fit well in Kraepelin's dichotomy of dementia praecox and affective disorder. However, this was not the perfect solution since criteria for diagnosing schizoaffective disorder were not firmly set at that time. The broad category of schizoaffective disorders included not only patients with co-occurring schizophrenic and affective symptoms but also other "atypical" psychoses. Over time diagnostic criteria became more defined but the original question still remains the same: is there any such thing as schizoaffective disorder? This paper presents some historical and modern data which may help clarify this issue, but it is still premature to give a definitive answer on all pending questions related to this interesting topic.