It is likely that the gender effect observable in case of 5-HTTLPR may be related to the effect of gonadal steroids influencing the expression of genes regulating serotonin synthesis and metabolism and removal of serotonin from the synapse and stimulation of pre- and postsynaptic serotonergic receptors.76, 77, 78, 79, 80 5-HTTLPR was also hypothesised to influence development of the serotonergic system in a gender-dependent manner,81 and, as the serotonergic system has a role in proliferation, migration, differentiation and synaptogenesis, establishment and function of brain circuits modulated by genetically based differences in serotonergic function may be different in men and women.66 It is also plausible that there are gender differences in responding with depressive symptoms to different stressors because different reproductive strategies are effective in the two genders.61, 82, 83
