Sex differences in depressive response during monoamine depletions in remitted depressive subjects

Although sex differences in the prevalence of depression are well known, the effects of sex on the underlying mechanisms of illness and on antidepressant action remain less clear. Tryptophan depletion and catecholamine depletion (via alpha-methylparatyrosine [AMPT] administration) are broadly utilized methods for studying the effects of the safe and transient reduction of serotonin and catecholamine neuro-transmission, respectively. The present study assessed the effects of sex on the mood response during acute monoamine depletion.

Data on Hamilton Rating Scale for Depression (HAM-D) scores during depletion tests were analyzed retrospectively in 59 subjects (41 women, 18 men) who underwent tryptophan depletion and 39 subjects (25 women, 14 men) who underwent catecholamine depletion. All subjects were in remission from a DSM-IV-defined major depressive episode. Data reviewed included subjects enrolled between November 1993 and November 1997.

Significant increases in HAM-D scores were observed in response to both depletion procedures, with a similar magnitude of change. Analysis of variance with repeated measures of HAM-D scores revealed a significant main effect of time for tryptophan depletion (F = 7.31, df = 3, p < .01) and for catecholamine depletion (F = 9.61, df = 4, p < .01). Time-by-sex interaction was significant for tryptophan depletion (F = 4.04, df = 3, p = .01), but not for catecholamine depletion (F = 0.75, df = 4, p = .57). Depressive symptoms were significantly greater in women during tryptophan depletion (t test p < .01), while no significant sex differences were found during catecholamine depletion.

These findings suggest that the effect of sex in depressive vulnerability may be related to differential sex effects in monoaminergic function.