Abstract
Evolutionary approaches to parental care suggest that parents will not automatically invest
in all offspring, and should reduce or eliminate investment in their children if the costs
outweigh the benefits. Lack of paternal or social support will increase the costs born by
mothers, whereas infant health problems will reduce the evolutionary benefits to be gained.
Numerous studies support the correlation between postpartum depression (PPD) and lack of
social support or indicators of possible infant health and development problems. PPD may be
an adaptation that informs mothers that they are suffering or have suffered a fitness cost, that
motivates them to reduce or eliminate investment in offspring under certain circumstances, and
that may help them negotiate greater levels of investment from others. PPD also appears to be
a good model for depression in general.
Keywords: postpartum depression, parental investment, life history theory, evolutionary
psychology, reproduction, mental health