Time points for assessing perinatal mood must be optimised

EDITOR—Evans et al studied perinatal mood using the Edinburgh postnatal depression scale.1 They claim that symptoms of depression are not more common or severe after childbirth than during pregnancy and that depression during pregnancy is more common than postnatal depression. These two findings have potentially far reaching implications, but caution is needed in using the data to draw these conclusions.

The Edinburgh postnatal depression scale has been validated for use only in the early postpartum period and predicts depression correctly in most (73%) women with a score above 12.2 Analysis of scores below this threshold should be made with care: variability of 1–2 points then has not been proved to indicate severity of depression. The interpretation of raised mean scores (such as 6.72 at 32 weeks of pregnancy compared with 5.84 at 8 weeks post partum) as indicating more severe depression may then be inaccurate. The difference in mean scores should be considered with respect only to those scores above 12, but the authors did not do this. Instead they evaluated change in average score.

Factors assessed by checklists of depressive symptoms tend to be associated with many psychiatric disturbances, including anxiety and related stresses such as adverse living conditions.3 Thus non-specific stressors leading to higher levels of anxiety could transiently increase a woman's score on the Edinburgh postnatal depression scale at any time. Two of the time points chosen (18 and 32 weeks of pregnancy) coincide with times of contact with staff for antenatal screening and discussion of the birth plan. Having to consider these choices adds to mounting anxiety secondary to many factors, including …