People addicted to methamphetamine may be helped by exercise along with addiction counseling, a new small study suggests. The researchers report exercise increased the number of dopamine receptors in the brain, which can lower the desire for the drug.

Using methamphetamine causes a release of dopamine, a substance in the brain that provides sensations of pleasure and satisfaction. It also causes methamphetamine’s high. Repeated meth use causes the number of dopamine receptors to decrease.

As a person recovers from meth addiction, the number of dopamine receptors increase over time, but the recovery rate varies widely. Other studies have suggested chronic use of meth can cause long-term problems in brain function that can affect a person’s self-control and judgment, the researchers said.

The eight-week study included 19 people addicted to methamphetamine, UPI reports. All of the participants received behavioral therapy for their addiction. Ten participants were asked to walk or jog on a treadmill three times a week for an hour, and to do resistance training for eight weeks. The other nine participants were given health education training, but were not advised to exercise.

Participants were given PET scans to determine the number of dopamine receptors in their brain. Those who exercised had a 15 percent increase in the number of dopamine receptors, compared with 4 percent in the education-only group.

The study appears in the journal Neuropsychopharmacology.

“Although this is a small study, it’s a very encouraging finding,” lead researcher Edythe London of the Semel Institute for Neuroscience and Human Behavior at UCLA said in a news release. “The results demonstrate that methamphetamine-associated damages to the dopamine system of the brain are reversible in human subjects, and that recovery of the dopamine system after chronic drug use can be facilitated with exercise training.”