CHICAGO (Reuters) - A significant number of U.S. veterans back from wars in Iraq and Afghanistan begin abusing alcohol after returning, perhaps to cope with traumatic memories of combat, military researchers said on Tuesday.

Younger servicemen and women, those who were previously heavy drinkers, and call-ups from the National Guard and Reserves were the most likely to increase their drinking and to develop alcohol-related problems, according to the study.

“Increased alcohol outcomes among Reserve/Guard personnel deployed with combat exposures is concerning in light of increased reliance (on these) forces” by the Pentagon, the report said.

“Active-duty Marines were also found to be at increased odds of continuing to binge drink after deployment, as well as to experience new-onset alcohol-related problems,” wrote Isabel Jacobs and colleagues at the Naval Health Research Center in San Diego, California.

Men were considered heavy drinkers if they consumed more than 14 alcoholic drinks per week, women seven drinks; binge drinking referred to downing five or more drinks in a day or occasion, four for women; and alcohol problems constituted drunkenness or hangovers that interfered with work or other responsibilities.

Reasons for the increased rates of alcohol abuse among Guard and Reserve members may be that they receive less training and support services than other arms of the military, they must transition from civilian life to a war zone, and their units are less cohesive, the report said.

The researchers surveyed 48,400 service members before (between 2001 and 2003) and after likely deployment (2004 to 2006) to identify heavy drinkers, binge drinkers, or those with alcohol-related problems.

Of those interviewed, 5,500 experienced combat and they were interviewed about a year after their return.

Combat veterans were 31 percent more likely to have begun binge drinking than those not exposed to combat. Six percent of returning combat veterans started a new habit of heavy weekly drinking and 5 percent developed a drinking-related problem.

New cases of alcohol abuse also arose among those who had not been deployed or did not see combat, but the rate of new cases was lower compared with returning combat veterans.

Women also had different drinking habits than men.

“Women were significantly more likely to start drinking heavily but less likely to start binge drinking or have alcohol-related problems compared with men, which may be due to women turning to drinking as a coping mechanism, whereas men may have a higher propensity for risk-taking behaviors,” the researchers wrote in the Journal of the American Medical Association.

The findings were consistent with a recent study of soldiers returning from Iraq that found 12 percent of active-duty personnel had alcohol problems, and 15 percent of Reserve and National Guard members did.

The researchers said they hoped to direct intervention efforts at younger soldiers and other groups prone to alcohol abuse. They also pointed to the need to treat post-traumatic stress suffered by returning veterans who may try to drown their memories in drink.