Unlike women, men are not generally brought up to express their emotions or ask for help. This can be especially problematic for new fathers, since the prospect of parenthood carries all kinds of insecurities: What kind of father will I be? Can I support my family? Is this the end of my freedom?

And there is probably more to male postpartum depression than just social or psychological stress; like motherhood, fatherhood has its own biology, and it may actually change the brain.

A 2006 study on marmoset monkeys, published in the journal Nature Neuroscience, reported that new fathers experienced a rapid increase in receptors for the hormone vasopressin in the brain’s prefrontal cortex. Along with other hormones, vasopressin is involved in parental behavior in animals, and it is known that the same brain area in humans is activated when parents are shown pictures of their children.

There is also some evidence that testosterone levels tend to drop in men during their partner’s pregnancy, perhaps to make expectant fathers less aggressive and more likely to bond with their newborns. Given the known association between depression and low testosterone in middle-aged men, it is possible that this might also put some men at risk of postpartum depression.

By far the strongest predictor of paternal postpartum depression is having a depressed partner. In one study, fathers whose partners were also depressed were at nearly two and a half times the normal risk for depression. That was a critical finding, for clinicians tend to assume that men can easily step up to the plate and help fill in for a depressed mother. In fact, they too may be stressed and vulnerable to depression.

And there is the child to think about. Research has clearly shown that maternal postpartum depression can impair the emotional and cognitive development of infants. A father could well buffer the infant from some of the adverse effects of maternal depression  but that is a tall order if he too is depressed.