For many parents, bringing a child into the world is the greatest journey, experience, and accomplishment of their lifetime. After dedicating those 9 months to growing a healthy baby, seeing their child and hearing them cry for the first time is an absolute miracle. The parents want nothing more than to take their newborn baby home and embark on the joys of parenthood.

But sometimes a feeling they can’t shake stops them in their path: a disease called postpartum depression. Postpartum depression makes parents feel sad, hopeless, and guilty because they either feel a disconnect with the baby or lose the desire to care for the baby. Insomnia, loss of appetite, and irritability typically accompany the harrowing illness as well.

While postpartum depression is typically thought to only affect women, a new study proves that it can also affect dads—depending on testosterone levels. According to the study, dads face a higher risk of developing the illness if their testosterone levels drop nine months after their baby is born. While this is bad news for the dad, it is actually—in a way—good news for the mom, as the study also found that women reported fewer feelings of depression themselves when their partner had these lower testosterone levels.

Unfortunately, high testosterone levels weren’t so good for the men either. Dads with higher levels of testosterone following the birth of their child experienced more stress from parenting and were more likely to act aggressively toward their partners.

This study, which was published in Hormones and Behavior, supports other studies that show men, too, experience their own biological responses to fatherhood. “We often think of motherhood as biologically driven because many mothers have biological connections to their babies through breastfeeding and pregnancy,” says Darby Saxbe, lead author of the study and an assistant professor of psychology at USC Dornsife College of Letters, Arts and Sciences. “We don’t usually think of fatherhood in the same biological terms. We are still figuring out the biology of what makes dads tick.”

In order to make these discoveries, the researchers looked at data from approximately 150 couples in the Community Child Health Research Network. This data looked at testosterone levels of the fathers nine months after the birth of their child, and also reported the couples’ answers to questions about depressive symptoms, as well as their relationship satisfaction, parenting stress, and aggression. Higher scores on the latter three subjects correlated with greater depression.

This new revelation in postpartum depression among males is a tricky issue to tackle, considering the negative effects of both high and low levels of testosterone. “One take-away from this study is that supplementing is not a good idea for treating fathers with postpartum depression,” said Saxbe. “Low testosterone during the postpartum period may be a normal and natural adaptation to parenthood.” She went on to say that some studies have shown physical fitness and suitable sleep help balance out hormone levels.

Darby E. Saxbe, Christine Dunkel Schetter, Clarissa D. Simon, Emma K. Adam, Madeleine U. Shalowitz. High paternal testosterone may protect against postpartum depressive symptoms in fathers, but confer risk to mothers and children. Hormones and Behavior, 2017; 95: 103 DOI: 10.1016/j.yhbeh.2017.07.014