The link between genes and life experiences

By | Science & Technology
The Brain. Credit@flickr user Ars Electronica.

A new study has found that mental health conditions may only be partially inherited and that individuals may be even more in control of these conditions than previously believed. This may give confidence to those affected by mental health conditions or those who have friends or family members who are affected.

A new study carried out in Victoria, Australia by Nguyen and colleagues was published in The British Journal of Psychiatry. This study adds to previous research on the link between genes and life experience.

If an individual experiences adversity during childhood this may be a factor necessary for developing mental health conditions later on in adulthood. However, some individuals experience adversity and sidestep the development of mental health conditions in adulthood.  It had been hypothesised that susceptibility may involve specific genes.

A specific gene 5HTTLPR may have been identified as a moderator of the relationship between mental health conditions and adverse life events.  Evidence shows the S-allele of this gene in combination with adverse experiences may be more likely to result in mental health conditions for an individual.  Meta-analyses, studies that combine data from large numbers of studies, only some have supported this idea.

The study by Nguyen and colleagues was designed and intended to be unique as participants were followed over a 5 year period, constantly re-assessing them. All participants provided a sample for DNA examination. This allowed the team to assess the interaction between the 5HTTLPR polymorphism (when two or more phenotypes exist) and adversity in childhood on the development of mental health conditions. The participants recruited all completed a questionnaire on mental health conditions and all 498 scored 16 or higher on a scale considered clinically relevant.

Serotonin molecule.  Credit @ Benjah-bmm27.

Serotonin molecule. Credit @ Benjah-bmm27.

 

All participants completed questionnaires every year on their symptomology in line with symptoms listed in the DSM-IV.  The child adverse experiences self-report (CMHSR) was utilised to measure individual history of childhood adversity. The 5HTTLPR polymorphism was analysed using a popular technique with slight adjustments.

The results showed that childhood adversity’s effect on the development of mental health conditions were moderated by the 5HTTLPR genotype. Participants with the s/s genotype had experienced childhood adversity and had significantly greater symptomology than those who had been adversity free.  Individuals with the l/s or l/l genotype had similar development of mental health conditions irrespective of adversity experienced in childhood. Interestingly, s/s carriers may have more beneficial symptomology in comparison to s/l and l/l carriers.

This demonstrates that dependent on the context an individual may experience, a gene may raise the chances of mental health conditions or be beneficial to the individual. Those with the s/s genotype with a lack of history of adversity may be more contented than the general population.  This evidence may be used in a positive manner to support the prescribing of medication to those with mental health conditions. It has been found that s/s allele carriers respond differently to medication in comparison to l/l carriers.  This may support medical professionals so that over prescribing medication, when there might be legible benefit to an individual using a different method, it’s circumvented.

A mixture of factors is necessary to increase the likelihood of developing mental health conditions. These include the s/s allele of the 5HTTLPR gene and particular adverse experiences. This may offer hope to those individuals with mental health conditions as the study showed that if that individual is placed into a supportive environment some may benefit and grow. This also may offer hope to carers, who may gain optimism from the idea that the conditions are fluid and far from inescapable.

How do genes and life experiences combine to influence mental health conditions?

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