A father's depression during the first years of parenting - as well as a mother's - can put their toddler at risk of developing troubling behaviors such as hitting, lying, anxiety and sadness during a critical time of development, according to a new Northwestern Medicine study.

This is one of the first studies to show that the impact of a father's depression from postpartum to toddlerhood is the same as a mother's. Previous studies have focused mostly on mothers with postpartum depression and found that their symptoms may impact their children's behavior during early, formative years.

"Father's emotions affect their children," said Sheehan Fisher, lead author of the study. "New fathers should be screened and treated for postpartum depression, just as we do for mothers."

Sheehan is an instructor in psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine and a psychologist at Northwestern Memorial Hospital. He conducted this study while he was a researcher at the University of Iowa.

The study was published online in the journal Couple and Family Psychology: Research and Practice.

Mothers and fathers who are depressed may not make as much eye contact or smile as much as parents who are not depressed. The more disengaged parents are from their child, the greater the risk the child will have forming close attachments and healthy emotions, Sheehan said.

"Depression affects the way people express emotions, and it can cause their behavior to change," Sheehan said.

Previous studies have shown that fathers are at a greater risk of depression after the birth of a child than at any other time in a typical male's life. This study found that a father's mood during postpartum is important to the trajectory of his depression three years later and significant for predicting his child's behavior during toddler years.

"Early intervention for both mothers and fathers is the key," Sheehan said. "If we can catch parents with depression earlier and treat them, then there won't be a continuation of symptoms, and, maybe even as importantly, their child won't be affected by a parent with depression."

Sheehan collected data from a cohort of nearly 200 couples with 3-year-olds. These couples had participated in a previous depression study around the time of their child's birth.

Questionnaires administered to the participants gathered information about parental depression, their relationship with their partner, and their child's internalizing behaviors (sadness, anxiety, jitteriness) and externalizing behaviors (acting out, hitting, lying). The questionnaires were completed by both members of the couple independently and mailed back to the investigators.