Monoamine Oxidase and Criminality: Identifying an Apparent Biological Marker for Antisocial Behavior

Abstract

After describing how monoamine oxidase (MAO) appears to affect brain functioning, and how the activity of this enzyme, in turn, seems to be influenced by hormonal and genetic factors, studies are reviewed which link low MAO activity with high probabilities of criminality, psychopathy, childhood conduct disorders, as well as with sensation seeking, impulsivity, and drug abuse (especially alcoholism). Overall, low MAO activity appears to be associated with restless and uninhibited behavior patterns, and may reflect some of the mediating effects of serotonin and sex hormones (especially androgens) on criminal behavior. Lower MAO activity is more characteristic of males than females, and appears to be lower in Blacks than Whites, and lowest during the second and third decades of life. Interpretations of the findings reviewed in this article must be cautious, and on guard not to exaggerate their relevance to criminal behavior, however, they are very encouraging to those seeking to find some of the neurological underpinnings of human variations in criminal behavior.