The psychosis continuum and categorical versus dimensional diagnostic approaches.

This overview briefly presents recent thinking on the dimensional approach to understanding psychotic experiences. First, evidence is provided for a continuum of psychosis ranging from self-reported infrequent psychotic symptoms in the general population, to schizotypal traits, to schizotypal personality disorder, and finally to full-blown psychosis resulting in a diagnosable primary psychotic disorder. Variation within each of these types of psychotic experience is discussed. Then, a comparison is presented between categorical and dimensional approaches to the diagnosis of psychosis by highlighting four advantages of each approach. In doing so, it is emphasized that the categorical approach is beneficial primarily in terms of reliability, whereas the dimensional approach would enhance validity.