In conclusion, our findings indicate that in spite of previous contradictory results the 5-HTTLPR genotype shows a strong interaction but only with selected types of life events, most robustly with life events related to financial difficulties and to a lesser extent life events related to illnesses and injuries in the development of depressive symptoms, although no such interaction was found between 5-HTTLPR genotype and life events related to intimate relationships or to social network problems. These results are notable, given that we found only a weak main effect for the 5-HTTLPR genotype on depression and a weak interaction effect that did not survive correction when life events were not separated according to type. Therefore, our results strongly argue for the mediating effect of 5-HTTLPR between certain types of life events and depression, and may help to elucidate why previous studies yielded conflicting results. Understanding the differential effects of different types of stressors and adverse events, and how these may be mediated by different genetic components in the development of depression would be crucial to identify novel targets for early prevention, screening and intervention as well, both on the psychotherapeutic and pharmacotherapeutic levels.
