Methamphetamine users tend to do things they would never have thought about if they were sober. Compounds in the drug impair functioning of the brain’s frontal lobe, which controls judgment, impulse control, and our ability to determine the consequences of a situation. A study out of the University of California, Los Angeles (UCLA) has revealed a meth user’s risky behavior is caused by a lack of sensitivity to risk and reward in the area of the brain that controls emotional decision-making.

"These findings suggest that circuit-level abnormalities affect brain function during risky decision making in stimulant users." lead researcher from UCLA, Dr. Milky Kohno, said in a statement.

Kohno and her colleagues recruited 25 methamphetamine users and 27 non-users to act as a control group. The research team used function magnetic resonance imaging (fMRI) to examine each participant’s neurological behavior at rest and when performing the Balloon Analogue Risk Task (BART), a test that involves pumping a balloon to increase to amount of money they make or cashing out to avoid popping the balloon.

People who used methamphetamine were less likely to earn money on the BART because of their risky decision to keep pumping the balloon. fMRI also showed a lack of sensitivity for risk and reward in the right dorsolateral prefrontal cortex (rDLPFC), the region of the brain responsible for emotional impulses. Researchers noted that chronic methamphetamine use and addiction are linked to abnormalities in the neural circuits that control risky decision-making. Since risky decision-making is targeted in addiction therapy, Kohno hopes the study will help addiction experts in developing more effective treatments for people struggling with methamphetamine abuse.

According to the National Institute of Drug Abuse, methamphetamine is a synthetic stimulant that acts on the central nervous system. Using methamphetamine increases the brain’s production of dopamine, a chemical involved in reward, motivation, pleasure, and motor function. Long-term use of the drug can result in anxiety, confusion, insomnia, mood swings, and violent behavior. It is also associated with symptoms of psychosis, such as visual and auditory hallucinations, paranoia, and delusions. Some chemical and molecular changes to the brain caused by chronic methamphetamine use can take over a year to reverse.

Source: Kohno M, et al. Imaging Examines Risky Decision Making on Brains of Methamphetamine Users. JAMA Psychiatry. 2014.