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MORE ON MAO
Psychopathic traits and monoamine oxidase (MAO) activity may be synergistic
risk factors for adult criminality, according to a recent Swedish study.
MAO is an enzyme involved in the metabolism of serotonin, and reduced levels
of serotonin are strongly linked to impulsive violence and a range of
behavioral disorders (See related article, CrimeTimes, Vol. 3, No. 2, Page 1).
P.O. Alm and colleagues studied the platelet MAO activity of 68 male former
juvenile delinquents and 32 controls. In addition, each subject was
evaluated using the Psychopathy Check List (PCL).
Juvenile delinquents who were later convicted of crimes as adults, the
researchers say, "were found to have higher Psychopathy Check List (PCL)
scores and lower platelet MAO activity than either juvenile delinquents who
were not registered criminals from the age of 15 years or non-criminal
controls." Although there was no direct correlation between PCL scores and
MAO activity, Alm et al. note that "among the 27 juvenile delinquents who
developed persistent criminality, 21 subjects (78%) had PCL scores greater
than 0 and low platelet MAO activity, while none of these persistent
criminals were characterized by a combination of zero PCL score and high
platelet MAO activity." Former juvenile delinquents with low MAO activity
had a fourfold increased risk of chronic adult criminal behavior when
compared to former delinquents with high MAO activity.
The researchers note that "low levels of platelet MAO activity can also be
found in socially well-adjusted and creative non-criminal subjects," and
speculate that reduced MAO activity may be linked to personality traits such
as sensation seeking and impulsiveness rather than to criminality itself.
They note, however, that "previous [study] results have indicated an
association between psychopathy/antisocial lifestyle and low levels of
platelet MAO activity."
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"Psychopathy, platelet MAO activity and criminality among former juvenile
delinquents," P. O. Alm, B. af Klinteberg, K. Humble, J. Leppert, S.
Sörensen, L-H. Thorell, L. Lidberg, and L. Oreland, Acta Psychiatr Scand,
94, 1996, pp. 105-111. Address: Per Olof Alm, Department of Clinical
Neuroscience and Family Medicine, Section of Social and Forensic Psychiatry,
Karolinska Institutet, Box 4044, S-141 04 Stockholm, Sweden.
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