title: The role of MAO in personality and drug use.
abstract: Monoamine oxidases, both MAO-A and MAO-B, have been implicated in personality traits and complex behaviour, including drug use. Findings supporting the involvement of MAO-A and MAO-B in shaping personality and in the development of strategies of making behavioural choices come from a variety of studies that have examined either prevalence of gene variants in clinical groups or population-derived samples, estimates of enzyme activity in blood or, by positron emission tomography, in the brain and, most recently, measurement of methylation of the gene. Most of the studies converge in associating MAO-A and MAO-B with impulsive, aggressive or antisocial personality traits or behaviours, including alcohol-related problems, and for MAO-A available evidence strongly supports interaction with adverse environmental exposures in childhood. What is known about genotype effects, and on expression and activity of the enzyme in the brain and in blood has not yet been possible to unite into a mechanistic model of the role of monoamine systems, but the reason for this low degree of generalization is likely caused by the cross-sectional nature of investigation that has not incorporated the developmental effects of MAO-s in critical time windows, including the foetal period. The "risk variants" of both MAO-s appear to increase behavioural plasticity, as supportive environments may particularly well enhance the hidden potential of their carriers. Importantly, male and female brain and behaviours have been found very different with regard to MAO×life events interaction. Future studies need to take into consideration these developmental aspects and sex/gender, as well as to specify the role of different types of environmental factors.
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Estonia; Psychiatry Clinic, North Estonia Medical Centre, Tallinn, Estonia. Electronic address: jaanus.harro@ut.ee.
authors.forename: Jaanus
authors.initials: J
authors.lastname: Harro
authors.affiliation: Department of Neuroscience, Pharmacology, University of Uppsala, Biomedical Centre, Uppsala, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Oreland
mesh_terms: D000818:Animals; D006801:Humans; D008995:Monoamine Oxidase / Q000235:genetics* / Q000378:metabolism*; D010551:Personality / Q000235:genetics* / Q000502:physiology*; D012727:Sex Characteristics; D019966:Substance-Related Disorders / Q000201:enzymology* / Q000235:genetics*
chemical_list: D008995:Monoamine Oxidase
keywords: Alcohol; Impulse control; Monoamine oxidases; Personality; Sex