Schizophrenia is a chronic and highly impairing condition that affects around 1% of the human population. Evolutionary theories lend support for the idea of a continuum approach to the diagnosis of psychosis. Subclinical psychotic-like experiences are relatively common in children and adolescents, occurring in about 17% of youths. The prevalence rate of psychotic symptoms in the general population is up to 8%, which is about ten times higher than the prevalence of diagnosed psychotic disorders. Some scientists have argued that there may be a shared genetic variation between illness and non-clinical psychotic- like symptom expression. The high prevalence of non-clinical psychotic symptoms in the population prompt neuroscientists to re-evaluate these symptoms in the light of evolutionary theory. The schizophrenia impaired physical health and reduced probability of reproduction raises an evolutionary puzzle. How does schizophrenia persist in the population at a stable prevalence rate? The question regarding what processes maintain the persistence of high heritable variation in relatively disadvantageous traits, such as schizotypy, in the general population, remains a universal challenge across the domains of psychiatric and evolutionary genetics. Furthermore, is there any link between the evolutionary persistence of psychosis in the population worldwide and the association of creativity with psychoticlike experiences in the general population? There has been a healthy debate on many hypotheses. One possibility is that schizophrenia remains in the human population because of shared genetic linkages to creativity. During last decade many scientists search the explanation for the evolutionary enigma of the persistence of schizophrenia, and the nature of its relation to creativity, although the notion that there is a heritable aspect of at least some aspects of high ability, including creativity, is going back at least to Francis Galton’s book Hereditary genius (1869). Neuroscientists also suggested that schizophrenia may emerge as a by-product of social cognition or that certain types of hallucinations could be viewed as evolutionary by-products of a cognitive system designed to detect threat. Some traits, such as schizotypy, may have an optimal level of expression that is advantageous within the community. However, this trait has adverse consequences for the psychotic person, which becomes, as Sebastian Faulks (2006) suggested, “the price we pay for being what we are”.

Key words: Schizophrenia, schizotypy, psychosis spectrum, psychosis continuum, psychotic-like experiences, evolutionary genetics, creativity.

O. Giotakos (page 316)

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