According to new research, regular marijuana users may have impairments in their brain’s ability to respond to dopamine, a chemical released by the organ that is involved in feelings of reward, among other functions.
Although the research can’t determine if regular marijuana use affects deficits in brain reward centers – or if they use it to compensate for a less reactive dopamine system – these results could help explain why those who smoke pot regularly are more prone to depression, anxiety, irritability and increased sensitivity to stress.
Led by Dr. Nora Volkow, director of the National Institute on Drug Abuse (NIDA) and supported by the intramural research program at the National Institute on Alcohol Abuse and Alcoholism, the study challenged 48 participants, 24 controls and 24 marijuana abusers, with a drug that elevates extracellular dopamine (DA). Researchers then compared the subjective, cardiovascular and brain DA responses to the drug between the controls and the regular users.
Although the baseline measures of the receptor availability did not differ between groups, the marijuana users showed obviously duller responses when given with the drug. Specifically, the marijuana users had significantly lower behavioral, cardiovascular and brain DA responses to the drug, including self-reports for high anxiety and restlessness and pulse rate and blood pressure.
In other words, the regular marijuana users were not as effected by the drug than the control group, meaning that this decreased brain reactivity may contribute to their increased stress reactivity and irritability, as well as their addictive behaviors.