The evolutionary context of postnatal depression.

"Postnatal depression" denotes the syndrome of dysphoria, debility, and anxiety that follows childbirth in about 10-20% of women (as variously estimated). Its etiology is seen to be lodged in a variety of psychosocial as well as biological factors, among which the isolating and pressured culture of contemporary society (especially for women/mothers) is commonly singled out as a powerful precipitator. This view is extended here through the evolutionary perspective which casts maternal distress as a set of adaptive responses with the function, in ancestral environments, of soliciting support for a mother who feels that her maternal responsiveness may be threatened. As continuous caretaking of the infant is the active expression of evolved maternal responsiveness, departures from this pattern result in anxiety and distress that seek resolution. Manifestations of maternal distress in contemporary society are dysfunctional, however, since the present social structure does not provide spontaneous and immediate support that can spring forth within small, closely knit social units. Furthermore, for present-day mothers distress is self-perpetuating since the ingrained tendency toward continuing responsiveness rarely finds practical expression and is thus converted into anxious vigilance and depression. This view generates the hypothesis that the emotional and cognitive contents of maternal vigilance are associated with the needs of the infant and will therefore be focused on crying and feeding. A number of qualitative studies of women's experiences during the postpartum bear out this prediction and support the feasibility of the evolutionary hypothesis of "postnatal depression" as a set of adaptive responses, now out of place in a novel environment.