Many mental-health problems have their origins in interactions between people's genes and their environment and depression is no exception. Researchers from Spain and the Netherlands looked into the inter-relationship between adverse childhood events, variations in genes called 5-HTT and Val66Met and depression. 5-HTT governs the level of a substance called serotonin which has been associated with mood and Val66Met regulates brain-derived neurotrophic factor (BDNF) a substance which plays an important part in supporting brain cells and the connections between them. 534 healthy people filled out a questionnaire about their depression symptoms, were asked about their childhood experiences and were tested for the two gene variations. Total childhood adversity, childhood sexual abuse, childhood emotional abuse and childhood emotional neglect were all linked to higher depression scores. The effect of childhood abuse was particularly strong on depression symptoms in people with variations in their 5-HTT and Val66Met genes.
Aguilera, M ... [et al] - Early adversity and 5-HTT/BDNF genes: new evidence of gene-environment interactions on depressive symptoms in a general population Psychological Medicine September 2009, 39(9), 1425-1432