Study posits genetic predisposition for watching violent TV

Children carrying a specific
variant of an ADHD-related gene are more likely to watch violent TV and play
violent video games, research suggests.

Children exposed to such media
violence are in turn more likely to show ADHD-related behaviours; but
the findings also suggest that this correlation is true for children who
do not carry the studied gene variant.

'Our results indicate that
children's violent media use is partly influenced by genetic factors. This
could mean that children with this gene variant are more likely to seek out
stimulating activities, such as violent television viewing and video game
playing',
commented Sanne Nikkelen, the first author of the study, from the
University of Amsterdam.

However, it is possible that
children with ADHD are simply more likely to use violent media, as
the study only checked for correlation between these two factors without
determining which factor influences the other. In addition, no direct
effects on ADHD behaviour patterns were observed due to the studied gene
variant; it only acted indirectly by enhancing the children's use of
violent media.

It has previously been shown that ADHD-related behaviours as well as media use are heritable.
This study is the first to suggest that use of violent media can be
thought of as an intermediate step between genetic disposition and ADHD.
A variant of the 5-HTT gene, previously linked to ADHD behaviour
patterns in context of interaction between children's genes and their
home environment,
was chosen to test this hypothesis.

The 5-HTT gene is involved in
regulation of serotonin in the brain, which in turn is important for
control of human emotions and impulses. Several variants of the 5-HTT gene
are known; the specific ADHD-linked variant, evaluated in this study, was
the long variant 5-HTTLPR.

The research was conducted on
a sample of 1612 children of Dutch origin, aged five to nine years.
The children's health was frequently examined by physicians at health
centres, their DNA was tested, and surveys on their use of violent media were filled out by their
parents. Correlations between the 5-HTTLPR gene
variant and use of violent media were determined.

In addition to the 5-HTT gene,
several other genes have been linked to ADHD. In the study,
the scientists also tested their hypotheses on a variant of another
ADHD-related gene, the DRD4, but found no correlations. The authors
concluded that more research is needed to answer questions about relationships
between genes, environment, such as exposure to media violence, and complex
behaviours, such as ADHD.

The study was published in the Journal
of Communication.