Defining psychosis: the evolution of DSM-5 schizophrenia spectrum disorders.

Descriptions of mental illness exist throughout recorded history. However, until the mid-twentieth century, there was no standard nosology or diagnostic standard for mental disorders. This limited understanding of these disorders and development of better treatments. As conditions such as dementia praecox and schizophrenia were being described, collaborative efforts were made in the twentieth century to develop the first Diagnostic and Statistical Manual of Mental Disorders (DSM). This review provides an overview of the history of psychiatric diagnosis with a focus on the history of schizophrenia as a diagnosis in the DSM. DSM-5 updates to diagnostic criteria for schizophrenia and related disorders are provided. Limitations to diagnostic validity and reliability are discussed in addition to changes in diagnostic approaches to schizophrenia spectrum and other psychotic disorders in an effort to improve diagnostic validity and reliability. The DSM-5 reflects the culmination of an ongoing collaborative effort to improve the diagnosis of mental disorders, and future research in Research Domain Criteria (RDoC) will help provide convergent validity when understanding and treating mental illnesses.