Evolution of schizophrenia

The evolution of schizophrenia refers to the theory of natural selection working in favor of selecting traits that are characteristic of the disorder. Positive symptoms are features that are not present in healthy individuals but appear as a result of the disease process. These include visual and/or auditory hallucinations, delusions, paranoia, and major thought disorders. Negative symptoms refer to features that are normally present but are reduced or absent as a result of the disease process, including social withdrawal, apathy, anhedonia, alogia, and behavioral perseveration. Cognitive symptoms of schizophrenia involve disturbances in executive functions, working memory impairment, and inability to sustain attention.^[1]

Given the high numbers of individuals diagnosed with schizophrenia (nearly 1% of modern-day populations), it is unlikely that the disorder has arisen solely from random mutations.^[2] Instead it is believed that, despite its maladaptive nature, schizophrenia has been either selected for throughout the years or exists as a selective by-product.