Especially because of the lack of clinical homogeneity within schizophrenia patients, opinions claiming that there should be subtypes of schizophrenia have been existing since Kraepelin. Nevertheless, diagnostic validity of schizophrenia subtypes in leading classification systems has been controversial. It can be asserted that the biological proofs are the most important references to strengthen the validity of a classification system.
The concept of “deficit syndrome schizophrenia” was introduced to identify a relatively homogeneous group within the schizophrenia patients, in terms of clinical signs and symptoms. This concept can be considered as a promising candidate for the attempts to identify subtypes of schizophrenia. In this review, the history of “deficit syndrome schizophrenia”, its clinical aspects and its diagnostic validity will be addressed shortly and then results of the biological studies about deficit syndrome schizophrenia will be evaluated, and by this way some information about the biological validity of this classification system will be presented.