Yükseköğretim Kurumları Destekli Proje, 2009 - 2011
Across the life span, stressful life events
influence the onset and cause of
depression. Diathesis-stress theories predict that individuals’
sensitivity to stressful life events depends on their genetic make-up. A functional
polymorphism in the promoter region of the serotonin transporter gene was found
to moderate the influence of life events on depression. Caspi et al (2003), showed that individuals with one or two copies of the short allele of the
serotonin promoter polymorphism exhibited more depressive symptoms
in relation to stressful life events than individuals homozygous for
the long allele. Our aim in this study was to retest if
serotonin transporter polymorphism was associated with stressful life events
and depression in Turkish population. Methods: 70 patients with major
depression (MD) and 55 age-sex-education matched healthy controls were
evaluated with SCID-I, Hamilton depression rating scale (HDRS), stresful life
events and childhood trauma questionnaire and temperemant and character
inventory (TCI). Results: Number of stressful life events in the
preceding year and their distress and
adaptation scores were significantly higher in the MD group. Likewise;
emotional abuse, emotional neglect and physical neglect scores in childhood were also significantly
higher in MD group. For TCI; novelty seeking and harm avoidance scores were
significantly higher but self-directedness scores were significantly lower in
the MD group. But, there were no differences in terms of either biallelic or
triallelic serotonin transporter genotyping between the two groups. In spite of
this, Beck depression inventory score, emotional abuse and emotional neglect
scores were found to be significantly higher in the SS genotype group compared
to LS an LL groups, although no difference could be found between the 3
genotype groups in terms of number of stresful life events in the preceding
year. Regression analysis revealed that
number of stressful life events in the preceding year and their distres score,
emotional abuse, emotional neglect and physical neglect scores predicted HAMD
score while serotonin transporter genotype did not have a predictor effect. Conclusion:
This is the first replication study from Turkey. Although we could not find
a difference in terms of serotonin transporter genotype, we showed that the
moderating effect of serotonin transporter polymorphism was greater for
childhood trauma than for stresful life events just before the onset of
depresssion like in other gene-environment interaction studies in major
depression (1,2). These findings might suggest an influence of serotonin
transporter polymorphism on serotonin transporter levels at an earlier phase of life, with the
possibility of a disruption of normal maturation of certain neural networks
which have an influence upon risk of depression independent of the current
state of serotonin function (3)