a1 Vivian M. Rakoff PET Imaging Centre, Centre for Addiction and Mental Health and Department of Psychiatry, University of Toronto, Toronto, ON, Canada
a2 Mood and Anxiety Disorders Division, Centre for Addiction and Mental Health and Department of Psychiatry, University of Toronto, Toronto, ON, Canada
a3 Clinical Research Department, Centre for Addiction and Mental Health and Department of Psychiatry, University of Toronto, Toronto, ON, Canada
a4 Max-Planck-Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
Background Monoamine oxidase A (MAOA) is an important enzyme that metabolizes monoamines such as serotonin, norepinephrine and dopamine in the brain. In prefrontal cortex, low MAOA binding is associated with aggression and high binding is associated with major depressive disorder (MDD) and also risk for recurrence of depressive episodes. In rodent models, low MAOA levels are associated with increased aggression and fear conditioning, and decreased social and exploratory investigative behaviors. Our objective was to measure MAOA binding in prefrontal cortex and concurrently evaluate a broad range of validated personality traits. We hypothesized that prefrontal MAOA binding would correlate negatively with angry-hostility, a trait related to aggression/anger, and positively with traits intuitively related to adaptive investigative behavior.
Method Participants were aged 19–49 years, healthy and non-smoking. MAOA binding was measured with [11C]harmine positron emission tomography (PET) in prefrontal brain regions and personality traits were measured with the NEO Personality Inventory Revised (NEO PI-R).
Results Prefrontal MAOA binding correlated negatively with angry-hostility (r=−0.515, p=0.001) and positively with deliberation (r=0.514, p=0.001). In a two-factor regression model, these facets explained 38% of variance in prefrontal MAOA binding. A similar relationship was found in prefrontal cortex subregions.
Conclusions We propose a new continuum describing the relationship between personality and MAOA: deliberate/thoughtful contrasting aggressive/impulsive. Additionally, the association between high MAOA binding and greater deliberation may explain why some people have moderately high levels of MAOA, although very high levels occur during MDD. In health, higher MAOA binding is associated with an adaptive personality facet.
(Received May 11 2010)
(Revised July 27 2010)
(Accepted July 28 2010)
(Online publication September 01 2010)