A study conducted at the University of Cambridge in the UK, involving 238 teenagers between the ages of 15 and 18 years, focused on investigating how GENES AND ENVIRONMENT INTERACT and in what ways this interaction increases or decreases an individual’s chances of being. diagnosed with depression in later life.
ABOVE : Brain scans reveal the dramatic difference in the activity levels in the respective brains of a depressed and a non-depressed individual.
In the study, the teenagers were put into six different groups; the group they were placed in was determined by two factors :
1) Whether or not they had experienced significant childhood trauma (eg exposure to family arguments, stress and other trauma) prior to the age of 6 years
2) Their particular type of genetic variation in relation to a specific gene involved in the production of serotonin in the brain (serotonin is a neurotransmitter – a sort of chemical messenger which helps cells in the brain communicate with one another – and affects our moods and emotional state).The teenagers all had one of the following 3 types of genetic variation:
a) SS (two short versions of gene)
b) SL (one short and one long version of gene)
c) LL (two long versions of gene)
RESULTS : Those who had been exposed to trauma before the age of 6 years were more likely to develop depression later on BUT ONLY IF THEY ALSO HAD A GENETIC VULNERABILITY (genetic vulnerability, the study found, was due to having the SS variation or SL variation of the gene, represented above by categories ‘a’ and ‘b’).
Specifically, it was found that exposure to discord between parents and/or neglect led to the individual :
i) having a high level of emotional sensitivity
ii) having greater difficulty processing their emotions
iii) having a tendency to respond especially badly to criticism
iv) being more affected by the emotional tone of other people’s voices.
According to the study, these four factors, in turn, make it more likely that the individual will later be diagnosed with depression.
Having both the SS or SL variation of the gene AND experiencing early trauma is associated with a higher probability of being diagnosed with depression later on in life.
HOWEVER: having the LL variation of the gene and experiencing early trauma is NOT associated with a higher probability of being diagnosed with depression later on.
THEREFORE: having the SS or SL variation of the gene makes the individual MORE VULNERABLE TO THE EFFECTS OF EARLY TRAUMA, thus making it more likely that the s/he will eventually be diagnosed with depression, whereas, HAVING THE LL VARIATION OF THE GENE SEEMS TO PROTECT THE INDIVIDUAL FROM THE EFFECTS OF EARLY TRAUMA.
It may be inferred, then, that neither early trauma alone, nor genetic vulnerability alone, are sufficient to make it more likely the individual will be diagnosed with depression. It seems, instead, it is how the relevant genes and early life experiences INTERACT that determines the likelihood that a particular individual will develop depression.
NB It should be noted that research such as that described above is at a relatively early stage and more studies need to be carried out in order to clarify, build upon and refine these findings.
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David Hosier BSc Hons; MSc; PGDE(FAHE).