How fitness fights addiction

Could going for a jog help undo a serious pot habit? A new study by the University of Sydney that's put a group of dependent cannabis users on a program of aerobic exercise will soon find out.

The hope is that regular exercise sessions that raise the heart rate and burn fat will help to tame the cravings and symptoms of withdrawal that can make it hard to quit any addictive drug.

"When you smoke a lot of weed every day your brain receptors become saturated with THC (tetrahydrocannabinol), the active ingredient in cannabis, but when you stop smoking these receptors become starved and you become anxious, irritable and depressed," explains David Allsop, Associate Professor of psychopharmacology at the University of Sydney.

But emerging research suggests that exercise that revs up the heart rate can trigger brain changes that may help take the edge off cravings. One is by activating natural "happy" chemicals called endocannabinoids that latch on to the same brain receptors as THC. Cardio exercise also boosts levels of nature's brain "fertiliser", a chemical known as BDNF (brain-derived neurotrophic factor) that enhances growth of brain cells in the part of the brain involved with mood.

Then there's what happens in the body of a pot smoker when aerobic exercise starts burning fat – it also burns off THC stored in body fat and releases it into the bloodstream, says Allsop.

"In theory it should go from the bloodstream to the brain receptors starved of THC and help soothe the cravings – that's one of the things we want to find out," he says.

The study is a sign of budding interest in the use of exercise to help treat drug and alcohol dependence by reducing cravings and the risk of relapse.

"People like the idea because it's free, it's healthy and it's a low-cost intervention that could work and we already know that exercise improves mood," Allsop says.

The appearance of exercise physiologists in some rehabs is another sign.

"The evidence is building to show that exercise can be effective for reducing cravings, reducing the numbers of substance-using days and improving rates of abstinence. But it needs to be implemented as part of the treatment program – not just 'we have a gym here you can use it if you like'," says Kirrily Gould, an accredited exercise physiologist who works with people overcoming drug or alcohol dependence at St John of God Hospital in Richmond.

Gould is also researching the use of exercise as an adjunct treatment for substance abuse and in her experience with clients at the hospital, a 20 to 40-minute workout combining aerobic and strength exercises significantly reduces alcohol cravings and improves anxiety and depression over a 14-day period.

"Exercise can help in a lot of ways. Not only can it work as a distraction but when people start feeling good as a result of physical activity, they may be less inclined to use drugs or alcohol. Many people in rehab also have other problems such as anxiety, depression and PTSD which can all be helped by physical activity," she says.

"Working out is also about dealing with discomfort – and blotting out discomfort can be a reason why people use drugs," says one 29-year-old who took up power lifting after leaving rehab two years ago. "It also helps you to think 'clean'. When you're using you're in a crappy state of mind, you're around smoking and bad food but working out regularly puts you in a clean state of mind that goes with looking after yourself. It's also very empowering because you feel you're achieving something."

"Although the evidence that physical activity can help with cravings looks promising, we still need more research. But the fact that that there's good evidence that exercise improves mental health is a good reason for implementing exercise programs in drug and alcohol treatment," says accredited exercise physiologist Dr Simon Rosenbaum, a lecturer in the School of Medical Sciences at the University of NSW.

That's one reason why Odyssey House, the drug and alcohol rehab in New York encourages residents to train for the New York Marathon – and why residents of Odyssey House in Eagle Vale, in NSW, have access to a fitness instructor twice a week.

Exercise programs can also be a good way to reach men who might be reluctant to get help for problems with mental health, Rosenbaum adds.

"Exercise isn't stigmatising – in fact it's destigmatising. So while some men may not want to engage with a mental health program, they might like the idea of turning up to an exercise program to get fitter."