Postnatal depression--aetiological factors. 
One hundred and forty-two women at six weeks postpartum were asked to complete Cox's Edinburgh Postnatal Depression Scale.  Thirty-eight scored positively for depression and 28 of these were followed up by a psychiatrist.  Twenty-eight controls were randomly selected from those who scored negatively.  Numerous variables were considered, including the type of labour, whether the mother was breastfeeding or not, and the presence or absence of a psychiatric history.  In addition the depressed group completed the Eysenck Personality Inventory.  A past psychiatric history was found to be a very significant risk factor and there is a definite association between postnatal depression and delivery by forceps, vacuum or caesarian section.  Maternal age and breastfeeding were not found to be of aetiological significance.