Everybody experiences stress, from the
small things, such as missing the train to work, to rather more difficult
situations, such as dealing with a car crash. The way that we deal and respond
to stress however, can vary from person to person. It is estimated that 10% of
people in the UK will experience Anxiety and Mixed Depressive Disorder at some
point in their lives. So why is it that our responses to stress can be so
different?
Anxiety disorders (such as
post-traumatic stress disorder, amongst others) can be exceptionally
debilitating in everyday life. People with anxiety disorders are also thought
to pay more attention towards negative or threatening things in the environment
around them and have been linked with a variation in the Serotonin Re-uptake
Transporter Gene (5-HTTLPR).
Serotonin (also known as 5-HT) is a
common and important neurotransmitter in the brain that is strongly linked with
mood. The short version (s allele) of the 5-HTTLPR gene causes lower production
of the Serotonin Transporter, which removes serotonin molecules from the
synapses between nerve cells after they have been used for signalling. Thus,
having the s allele will cause increased levels of serotonin in the synapse,
due to slower re-uptake.
 |
| Serotonin is a monoamine neurotransmitter. |
A study published last month, has looked into effects of the s allele on attention bias. They split their participants into two groups, with roughly a 50/50 split of people with the s allele and the long (l) allele. The groups were then subjected to an attention bias test, before undergoing attention bias modification (ABM). ABM is an experimental technique that is used to alter a person’s attention bias, either more positively or negatively, reflecting encounters with positive and negative stimuli in our everyday lives.
Participants with the s allele were
more sensitive to ABM, scoring higher in both positive and negative attention
bias tests after the ABM, but were especially sensitive to negative stimuli.
This result suggests a role for 5-HTTLPR as an ‘adaptability gene’, ie, not a
gene that would affect us all the time, but given the right stimuli,
could be responsible for changes in the way our brain works that would affect
our response. In practical terms this shows that people with anxiety disorders
may be predisposed to dealing poorly with stressful life events, but that they
may also thrive in an environment that is supportive.
It also shows the possible importance
of Gene/ Environment interactions (GxE). This is an area for debate in current
research but it seems clear that in some cases it is not simply the genes you
possess that is the most important factor, but how they interact with the
external stimuli that we encounter.
This paper suggests the possibility of
serotonin- reducing drugs possibly being effective in an anti- anxiety setting.
Clearly we will need further research to find an effective treatment.
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