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One emerging aspect of recent advances in neurocriminology is the discovery of possible
links between violent criminal behaviour and genetics. Analysis of data from several
studies indicates that the strongest link between genetic variation and aggression
comes from monoamine oxidase A (MAOA); a gene encoding an enzyme responsible for catabolising
amine neurotransmitters such as dopamine, serotonin and noradrenaline. In this work,
we present a critical review of the data available from recent investigations regarding
the impact of an allelic variation of the MAOA gene on criminal behaviour.
The main approach used in this work was reviewing and analysing data presented in
a variety of research papers accessed through electronic search.
The low activity form of the MAOA gene (MAOA-L) has been linked to increased levels
of aggression and violence. Data from a 2007 study suggests that MAOA-L individuals
are hypersensitive, so are affected more by negative experiences (thus react more
aggressively in defence) as opposed to being hyposensitive, and lacking emotion for
harming others. Male members of a large Dutch kindred displaying abnormal violent
behaviour were found to have low MAO-A activity linked to a deleterious point mutation
in the 8th exon of the gene. The unaffected male members within the family did not
carry this mutation. The first study that investigated behaviour in response to provocation
showed that, overall, MAOA-L individuals showed higher levels of aggression than MAOA-H
(high MAOA activity) subjects. There was also strong evidence for a gene-by-environment
interaction as both groups showed similar low levels of aggression with low provocation,
but MAOA-L individuals displayed significantly higher levels of aggression in a high
provocation situation. A further gene-by-environment interaction was found in a long-term
study performed on large number of children. Those with the MAOA-L genotype paired
with maltreatment in childhood were correctly predicted to commit crime. Similar results
are replicated in the majority of other related studies, but not all.
We present mounting evidence that biological, environmental, and social factors are
involved in criminal behaviour. Deficiencies in MAO-A activity have been identified
in numerous studies to correlate positively with aggressive behaviour, but its influence
may be moderated by environmental factors. Although further research into this aspect
of neurocriminology is required, the findings highlight an ethical dilemma with regards
to prosecuting criminals. Since individuals cannot be held accountable for their genes,
should they be held responsible for their dispositions and resulting actions?
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International Conference for Healthcare and Medical Students (ICHAMS) 2013