Mental health disorders

Abstract

Abstract This chapter discusses evolutionary explanations of mental disorders. The null hypothesis is that a person with a mental disorder is in the tail of a distribution of states whose central region contains people with normal function. Other hypotheses are that mental disorders are exaggerations or disruptions of adaptations, that they are disruptions of homeostasis produced by mismatch, and that they are exaggerations of normal defense responses. Disorders that may be explained by these hypotheses include anxiety, obsessive–compulsive disorder, and depression. The smoke detector principle may explain phobias and panic attacks. Drug addiction may be explained by the hijacking of the innate reward system by compounds not encountered in our evolutionary history. This chapter explores the hypothesis that autism and schizophrenia lie on opposite ends of a single spectrum on which the position of an individual is influenced both by copy number variation and by parent–parent conflict over infant growth mediated by genomic imprinting. Evidence supports some contribution of those mechanisms to both disorders.