Schizophrenia Spectrum and Other Psychotic Disorders

Schizophrenia spectrum disorders are characterized by the presence of delusions, hallucination, disorganized thinking, motor abnormalities, and/or negative symptoms. Behaviourally, schizophrenia patients have profound difficulties in regulating approach and avoidance, causing social withdrawal or aggressive behaviour. Evolutionary hypotheses of schizophrenia abound, but none covers all phenotypic aspects of the syndrome(s). Genetic risk for schizophrenia is partly conferred by genes that have undergone positive selection, whereby the reproductive advantage compensating for the reduced fecundity is as yet unknown. Environmental risk factors for schizophrenia comprise poverty, migration, and urbanicity, which has given rise to the hypothesis that individuals with schizophrenia are particularly sensitive to the exposure of strangers. In a more general vein, many signs and symptoms associated with schizophrenia can be interpreted from an evolutionary point of view. They pertain to diverse aspects of social life, including cooperation and trust (paranoia), mating (delusional jealousy, erotomania), and social rank (catatonic stupor, mutism).