Exercise might help people who are battling addiction stay on the straight and narrow, a new research review finds.

Investigators who analyzed 43 studies from around the world found a link between physical activity and reduced substance use among people in treatment for alcohol and drug abuse.

The idea for the study review "came to me when I was working as a kinesiologist in a therapy house for people with substance use disorders, and realized that physical health was not considered at all in these treatments, although the need was enormous," explained study lead author Florence Piché. She is a doctoral candidate in sciences and physical activity at the University of Quebec in Trois-Rivières and the University of Montreal, in Canada.

"We can assume that the mechanisms are multiple and multifactorial," Piché said of the findings.

The amount of exercise involved wasn't overwhelming. Most of the studies focused on the potential benefit of "moderately intense" activity, conducted for about an hour three times a week over the course of approximately three months.

Would more exercise confer greater benefits? Piché noted that none of the studies assessed that.

Collectively, the studies included just over 3,100 participants. They looked at the relationship between exercise and the risk of using heroin, opioids, cocaine and crack cocaine, methadone, marijuana, alcohol or methamphetamines. None involved cigarette smoking.

Half of the investigations evaluated exercise's relationship to total abstinence or reduction in substance misuse. Among these, 75% found that substance use fell in connection with physical activity.

Fourteen studies looked at aerobic activities, and 71% of these concluded aerobic exercise appears to help patients maintain their resolve to cut back or quit.

Twelve studies additionally reported a link between exercise and a reduction in depression-related symptoms.

Connie Diekman is a food and nutrition consultant and former president of the Academy of Nutrition & Dietetics.

"Participating in physical activity does increase people's goals to be healthy. It can also generate a 'euphoric'-type feeling. And it provides some structure to our daily lives. All things that can help us feel more in control of emotions and any need for substances to manage daily life issues," Diekman said.

"The overall conclusion was that exercise does appear to have a significant protective effect when it comes to reducing substance use among patients struggling with substance use disorders," according to Diekman, who was not involved in the review.

"The caveat," she added, "is that more studies are needed," given that smoking wasn't considered and many of the investigations had design flaws "making a clear cause-and-effect outcome hard to declare."

Also, aside from the one-third of the studies that focused on aerobic activity, Diekman noted that the team did not break down how different types of exercise might variously impact addiction.

Forty percent of the studies included in the analysis were done in the United States. About one-quarter were launched in China, and about 8% in northern Europe.

The findings were published online April 26 in PLOS ONE.