Researcher Given Grant to Further Study Effect of Exercise on Addiction

In a series of experiments over the last three years, Mark Smith, Associate Professor of Psychology at Davidson College, has found that exercise can reduce the desire for cocaine in addicted rats. Now he’s been given a grant of nearly $1 million from the National Institute on Drug Abuse to further investigate the benefits of exercise at various stages of addiction.

In the experiment, Smith tested the motivation of rats to push a lever to receive a dose of cocaine. Rats who regularly exercised gave up when they didn’t receive a dose after an average of 70 pushes. Those who were denied exercise kept pushing the lever an average of 250 times.

Now Smith seeks to find out whether exercise can help people avoid beginning drug use, whether it will lessen the amount of drugs new users employ, whether it can help people kick an existing habit, and whether it can help those in recovery avoid a relapse. He also seeks to find out whether exercise causes any physiological changes in the brain that "immunize" a person against drug abuse.

"We’ll be looking at exercise as both a preventative and treatment intervention," Smith said.

The grant will allow Smith to hire a full-time research technician, and Davidson College will provide two student assistants each summer. The grant will cover the cost of rats, and various types of existing and newly conceived chambers in which to house and exercise them. A colleague at Wake Forest University, Dr. David Roberts, will consult with Smith in designing and building a new type of chamber that allows rats concurrent access to both a running wheel and self-administration of drugs.

The chambers Smith has been using give rats access only to either the running wheel or drug self-administration. Smith believes that the new chamber more closely resembles real-world situations. "Addicts generally have the opportunity to choose between taking drugs or exercising. Maybe when our rats are in that situation they’ll choose the running wheel and won’t want to use cocaine. That’s what I’m hoping," he said.

Smith said he believes the effects of exercise on the brain are similar to the effects of cocaine. Both increase concentrations of the neurotransmitter dopamine, which is believed to contribute to the "runner’s high" people achieve when exercising.

Smith explained that addiction occurs when people use drugs because the substance "hijacks" the neural pathways in the brain that are responsible for human survival behaviors. Drugs provide the same rewarding feelings that humans get from food, water, and sex. But drugs are stronger, and much more effective in mimicking these natural rewards than the brain’s own chemistry. Over time, individuals become more sensitive to the drugs and less sensitive to the natural chemistry, causing them to abandon their social, occupational, and family responsibilities in the quest for another high.

While some drugs can help users overcome some forms of addiction, Smith doubts that an anti-cocaine pill will ever be discovered. "For heroin there’s methadone, for nicotine there’s Chantix, and for alcohol there’s naltrexone," he said. "But I think people will need some form of behavioral intervention for continued improvement with cocaine addiction."

Though his experiments will primarily focus on cocaine, later in the project Smith will also examine heroin, which has a similar effect on neural pathways.

He noted, "As a potential intervention (exercise is) free, it’s simple to administer, and it’s feasible for use in a large population of individuals. The principal side effects are improved cardiovascular health, reductions in depression and anxiety, and improvements in physical appearance. You’ve got to admit that’s an excellent intervention regardless of the disorder!"

Smith recently received an additional $50,000 grant from the American Reinvestment and Recovery Act to investigate whether simply socializing can help people overcome addiction. He’ll construct a large chamber in which two animals can live together and self-administer drugs simultaneously to determine whether peer contact influences drug use. "What happens if one rat is not given access to cocaine?" Smith said. "Does having an abstaining roommate reduce your own drug intake?"

"Three percent of Americans use cocaine at least monthly, and like most Americans I have friends and have known others who struggled with drug addiction at one point in their lives,” Smith said.

"There are a multitude of both genetic and environmental determinants in drug abuse. As a consequence, you’re going to need a large arsenal of interventions to combat the disorder. Better medications will be developed, but I think the best results will occur with behavioral interventions through psychotherapy and regular exercise,” he continued.

A former British drug addict sent Smith an e-mail that read in part, "A couple of years ago I was a regular cocaine user and occasional user of other recreational drugs. I fell into a bit of a hole and it was something I was not proud of, as I had been a very promising athlete when I was younger…However, about 9 months ago I decided to take up running again and I threw all my efforts into training. After a mere few weeks all my energy was being thrown into training and I was not even tempted by any drug on a night out…Now I am completely addicted to athletics again. I think your research is hugely important and I think something as simple as encouraging the young or even the addicts into exercise could transform their lives. It is so simple and I am so glad people such as yourself are trying to spread the word and put your energy into such research."