IN 2005 and 2006, in northern Pakistan, some 900 pregnant women took part in an unusual experiment. All were in their third trimester and suffering from depression. Most families in the area rely on subsistence farming. Almost none of the women worked outside the home. This kind of life is hard. Perinatal depression (depression around the time of giving birth) is more common in poor countries than in rich ones.

As part of one of the largest psychotherapy trials ever run, the women were split randomly into two groups. Those in one received weekly visits from a health worker for the month before the birth, and less frequent visits during the ten months after. The rest received the same number of visits, but from health workers who had been trained to deliver cognitive behavioural therapy (CBT) during the visits, too.

CBT is a talking therapy that aims to break the cycle of self-reinforcing negative thoughts. It focuses on the present, rather than trying to uncover the causes of deep-seated neuroses. Subsistence communities are a good place to test it, since no other mental-health services are in place.

The study was a success on its own terms, with the rate of depression falling by 73% for the mothers who received CBT compared with 41% for the rest. But in 2013 a team of researchers returned to measure the long-term impact on the women’s finances. It was surprisingly large. The results, currently under review at the journal of the Institute for Labour Economics, show that the women who received CBT in 2005-06 were 17% more likely than the rest to have control over their households’ spending. They spent more time with their children and were more likely to send them to private schools.

According to Victoria Baranov of the University of Melbourne, who worked on the study, the reason is probably that those mothers have more bargaining power within their households. “Depression might make you less able to advocate for your own interests,” she says. And the effects were stronger in mothers of girls than of boys, suggesting that mentally healthier mothers were able to lessen the harm suffered by daughters in a patriarchal society. She thinks CBT may be a more effective intervention than cash transfers, since it does not disrupt local social norms. It may not give a mother new options, but helps her choose better from those she does have.