Here's how swings in dad's testosterone affect family

Testosterone levels not only signals paternal postpartum depression, but may also indicate a more satisfactory relationship for mothers, a recent study has found.

Postpartum depression is often associated with mothers, but a new study shows that fathers face a higher risk of experiencing it themselves if their testosterone levels drop nine months after their children are born.

The same study revealed that a father's low testosterone may also affect his partner - but in an unexpectedly positive way. Women whose partners had lower levels of testosterone postpartum reported fewer symptoms of depression themselves nine and 15 months after birth.

High testosterone levels had the opposite effect. Fathers whose levels spiked faced a greater risk of experiencing stress due to parenting and a greater risk of acting hostile- such as showing emotional, verbal or physical aggression - toward their partners.

The findings support prior studies that show men have biological responses to fatherhood, said lead author Darby Saxbe.

"We often think of motherhood as biologically driven because many mothers have biological connections to their babies through breastfeeding and pregnancy." Saxbe said. "We don't usually think of fatherhood in the same biological terms. We are still figuring out the biology of what makes dads tick.

"We know that fathers contribute a lot to child-rearing and that on the whole, kids do better if they are raised in households with a father present," she added. "So, it is important to figure out how to support fathers and what factors explain why some fathers are very involved in raising their children while some are absent."

The study appears in the journal Hormones and Behaviour.