According to some UCLA researchers, early family experiences can reverse the outcome for people genetically inclined towards depression. A supportive family significantly reduced an individual’s likelyhood of developing depression.
From a medicalnewstoday.com article:
Among the study’s implications is that the short form of the 5-HTTLPR is “highly responsive to environmental influence” and, rather than predicting risk for depression, its effects vary substantially, depending on how supportive the external environment is…
Will Meek from the World of Psychology blog has a great post on it here.