In the days after his son was born, Rob Sandler found the thrill of becoming a new father replaced with dark feelings of dread and hopelessness. Those feelings, coupled with sleep deprivation and stress, culminated in a panic attack during his son’s bris.

As a group of old friends was saying goodbye after the ceremony, “I had this feeling that they were leaving and I was stuck in this situation that would never get any better,” said Sandler, a marketing executive in Dallas. “I just felt trapped.” What followed was months of sadness, anxiety and — perhaps most worrisome of all — a feeling of acute disappointment in his own ability to be a good parent.

In recent years, a growing body of research, and the increasing visibility of dads like Sandler, has given rise to the idea that you don’t have to give birth to develop postpartum depression, the so-called baby blues. Studies suggest that the phenomenon may occur in 7% to 10% of new fathers, compared with about 12% of new mothers, and that depressed dads were more likely to spank their children and less likely to read to them.

Now, a University of Southern California study has found a link between depression and sagging testosterone levels in new dads, adding physiological weight to the argument that postpartum depression isn’t just for women anymore. The study also found that while high testosterone levels in new dads helped protect against depression in fathers, it correlated with an increased risk of depression in new moms.

“We know men get postpartum depression, and we know testosterone drops in new dads, but we don’t know why,” said Darby Saxbe, a professor of psychology at USC and an author of the new report. “It’s often been suggested hormones underlie some of the postpartum depression in moms, but there’s been so much less attention paid to fathers. We were trying to put together the pieces to solve this puzzle.”

The idea that parents who haven’t given birth can get postpartum depression isn’t entirely new. Studies have shown, for example, that moms and dads who adopt children also show signs of the condition.

But some mental health experts question whether what fathers experience after birth is truly postpartum depression.

“There’s no question the perinatal time is one of the hardest for both men and women,” said Dr. Samantha Meltzer-Brody, a professor of perinatal psychiatry at the University of North Carolina School of Medicine. “But the process of birthing and the hormonal gymnastics that women experience is on a different planet.” When it comes to depression in dads versus moms, “I see them as utterly apples and oranges,” she said.

Indeed, defining postpartum depression has been a centurieslong pursuit, hobbled by a social stigma that prevents many women from acknowledging they have a problem. Women plagued by the sadness, anxiety and suicidal thoughts associated with the condition — first noted by Hippocrates in 400 B.C. — have long been told it was all in their heads, or blamed themselves for not being good enough moms.

In the past five years, several studies have shown evidence of a long-suspected link between postpartum depression and the hormonal fluctuations common to women after birth, bringing greater medical legitimacy to the diagnosis. Some of the shame and stigma surrounding the condition has also lifted as high-profile mothers like Brooke Shields, Gwyneth Paltrow and, most recently, Ivanka Trump have shared their own stories of postpartum depression.

Yet researchers still can’t say how large a role hormones may play relative to other factors like stress, sleep deprivation and a history of mental illness.

“What I take issue with is the contention that men don’t go through the wild hormonal changes” that women do, said Will Courtenay, a psychologist and author of “Dying to Be Men: Psychosocial, Environmental and Biobehavioral Directions in Promoting the Health of Men and Boys.” “It’s not just testosterone” that fluctuates in new fathers, he noted, “but also other hormones that we know are associated with births in women,” including estradiol and prolactin, he said.

And women are hardly alone in facing the stigma surrounding mental illness.

“There is a very powerful myth in this country that men don’t get depressed, or if they do, they shouldn’t express it,” said Courtenay. “Consequently, men are less likely to get treated for depression.”

To wit: Adam Busby, a father who appeared on the TLC reality series “OutDaughtered,” faced criticism in July after he went public with his depression following the birth of his quintuplets.

In 2007, Courtenay established Postpartummen.com as a gathering place for new dads struggling with mental health issues. Today, the site offers resources for men in search of assistance. Postpartum Support International also hosts a free phone consultation for dads on the first Monday of every month.

What both sides agree on is that too little attention has been paid to the role of men in the postpartum discussion. Dr. Jennifer L. Payne, director of the Women’s Mood Disorders Center at Johns Hopkins School of Medicine, said the new research helps shed light on the role that spouses and hormones may play in the condition but stopped short of labeling what men experience as postpartum depression.

The USC study, she said, “was about depressive symptoms, and I would not call that postpartum depression. I think that’s a very different ballgame.”

Saxbe isn’t so sure.

“To a certain extent, any postpartum depression is just depression that happens to emerge in the postpartum period,” she said. “It’s not super conclusive that there’s an obvious hormonal reason in women, either.”

Sandler, now 45, sees things differently. After his panic attack, he sought help from a psychiatrist, who prescribed medication and helped him see that his son’s “difficult infant phase” wouldn’t last forever.

“After three months, I started coming around,” he said. He credits the medication for helping ease his anxiety — “It helped not having those peaks and valleys” — and his “very supportive wife” for helping him focus on the joys of having a baby.

Since then, fathering “has been a wonderful experience,” he said.

Does he believe he had postpartum depression?

“I don’t want my experience to take away from anything a woman goes through,” he said. “This is nowhere in the same category.”

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