5-HTTLPR is a functional repeat length polymorphism influencing serotonin reuptake efficiency and consequently serotonin availability in the synaptic cleft in the central nervous system. The short (s) allele, associated with reduced efficiency of transcription of the serotonin transporter protein, has been found to predispose to various depression-related constructs2, 3, 4, 5, 6, 7, 8 and depression itself9, 10 in several human and animal studies.11 An initial large-scale follow-up study by Caspi et al. indicated a key role for the s allele of 5-HTTLPR in mediating the effects of stressful life events in the development of depression.1 This was followed by a number of contradictory replication studies and meta-analyses,12, 13, 14, 15 with the latest and most comprehensive meta-analysis once again supporting such an association.16 In the background of contradictory results, one of the more commonly proposed reasons was the lack of stratification according to the timing of negative life events. When categorised into early childhood and recent life events, an association between the 5-HTTLPR s allele and early-life adversities, but not recent life events, was found with depression.15, 16, 17,
