The day’s work was in full swing, the men in the platoon needed a break, and one of them began imitating his leader’s style of walking. Head down, elbows flapping, legs flying forward, he soon had the other soldiers laughing.

The "rhino walk," they called it, and it was a way to ease the tension of long days in southern Kandahar province. The platoon leader loved it, too, at first. "I thought the rhino walk was funny, and totally true; they got me," Lt. Courtney Wilson, who served in Afghanistan in 2010 and 2011, said in a recent interview.

But by the time she was in her bunk, she wondered. "Was it just being funny, or were they getting exasperated with me? That was the hard part," she said. "I started feeling a little like it was me versus them. I was worried the men didn’t like me. I wasn’t sure if they were making me one of the guys, or completely disrespecting and making fun of me."

In the months to come, that sense of exclusion would deepen into depression.

One of the biggest adjustments the U.S. military attempted during the Iraq and Afghanistan wars was cultural: the integration of women into an intensely male world. Women made up about 15 percent of the force during these two wars, compared with 7 percent in the Persian Gulf war of 1991, and they saw more combat in greater numbers than ever before.

Yet even though women distinguished themselves as leaders and enlisted soldiers, many of them describe struggling with feeling they do not quite belong. For men, the bonds of unconditional love among fellow combatants – that lifeblood of male military culture – are sustaining. But in dozens of interviews with women who served, they often said such deep emotional sustenance eluded them.

The psychic distress is measurable. More than 38 percent of women report depressive symptoms after deployment, compared with about 32 percent of men, according to a study published by the Journal of General Internal Medicine. Women are 10 times more likely than men to have reported serious sexual harassment. Suicide has been an enormous issue across the military, particularly for white men. But Army data show that the suicide rate for female soldiers tripled during deployment, to 14 per 100,000 from 4 per 100,000 back home – unlike the rate for men, which rose more modestly.

"Clearly these data beg us to account for why there’s this apparent surge in felt hopelessness and alienation among so many women service members during deployment," said Dr. Loree K. Sutton, a retired brigadier general, a psychiatrist and commissioner of the New York City Mayor’s Office of Veterans’ Affairs. "This is a critical endeavor, and it’s got to go beyond individual factors and look at group dynamics."

Wilson arrived in Afghanistan on April 1, 2010, landing at Kandahar Airfield – a dusty, chaotic staging area, swarming with convoys and contractors.

Soon she was leading a platoon in the 864th Engineer Battalion on projects in the Kandahar region and beyond. Her team moved heavy equipment; built security towers, barriers and fences; shored up roads and buildings; and leveled terrain for construction crews.

"You try moving 40-foot flatbeds full of equipment through those narrow dirt streets full of mud buildings without ruining anyone’s house," said Lt. Nicholas LaPonte, who later inherited her job. Running the platoon, he said, "means you’re up 20 hours a day, you’re planning missions, you’re on the move all the time."

As social scientists have sought to understand the increased rates of depression and suicide among enlisted women, they have looked at research on other groups at the margins of a culture, whether blacks in the Ivy League, whites attending a nonwhite high school – or women in male professions. And they have found that the mental costs borne by those in the minority are similar.

"Every bad thing that happens, they interpret it as a sign that they don’t belong," said Gregory M. Walton, an assistant professor of psychology at Stanford University. That uncertainty is likely to become especially predictive of mental trouble during deployment, he added, "when the unit becomes all-encompassing, the social network contracts."

Researchers are now asking how much "all those little things" – the differences inherent in being on the margins of a culture – affect a person’s mood, especially under the stress of combat.

Female veterans said in interviews that the expectations for male soldiers were clear: Do your part, keep your head, cover your buddy’s back – and you’re in.

In contrast, the women said, they got mixed messages. The Army bans most jewelry and makeup yet is institutionally protective toward women, at least out in the field. "You’re treated like a girl, and yet you can’t really be a woman – that’s the feeling," Wilson said.

One low point came one night in November 2010 when mortars rocked her base in Kandahar. As she squeezed into a cramped bunker with dozens of other soldiers, she felt no adrenaline rush, no fear, no concern for herself. She had gone dead empty.

"All around me, guys were calling home, calling other soldiers, checking on people to see if they were OK," Wilson said. "I was just standing there, numb, thinking, ‘OK, maybe now is when I die … hmm, that’s interesting.’

"I didn’t care whether I lived or died."

Out of Afghanistan, Wilson began suffering panic attacks, bursts of anxiety that squeezed her throat. "It got to where I couldn’t breathe, like I was close to blacking out," she said.

Jack Daniel’s and Coke blunted the anxiety, but the relief did not last. She tried biofeedback, prayer, meditation and psychiatric medications. Finally, reluctantly, she began talk therapy with a psychologist at Fort Hood in Texas.

"She really struggled to connect with other people, and in part it’s because she was trying to be someone she was not," Roger Belisle, a clinical psychologist at Fort Hood’s Resilience and Restoration Center, said in a phone interview.

That type of person – high expectations, tough on others, tougher on oneself, averse to asking for help – is a well-worn military role that is hard enough to fill for men. For women, it is an invitation to isolation, psychiatrists said. The best fighters are fierce, but they have a deep well of support from buddies.

Like Wilson, many women in the military did not have that kind of love. "It’s like, I got all the downside of serving in the Army and none of the upside, the camaraderie," Wilson said.

Out of the service, she is now in close contact with her friends, her parents and her brother. Whenever her mood wavers, she phones one of them – "therapy time," she calls it. In a final session, her therapist, Belisle, asked: What is your passion, right now?

"Travel," she answered.

"Then do it."

In August, Wilson finished her contract with the Army. On Oct. 29, after visiting with her brother and parents, she flew to Madrid.

She was determined to visit India and Africa, before returning. Or not.

This time the mission was open-ended, and the goals much harder to measure.

© 2015 The New York Times Company