Impulsive Behavior Found in Regular Marijuana Users

All marijuana users exhibit increased levels of impulsive behavior after consuming the drug, a new study examining the use of both it and cocaine revealed.

Designed to put to the test claims that increased impulsivity after marijuana use did not occur in regular users, the study offers evidence as to why drug use may trigger addictive behaviors.

The study, published in the British Journal of Pharmacology, looked at 61 healthy regular marijuana and cocaine users who were given both drugs and a placebo at different times before taking part in tests that challenged them to reflect before acting. The researchers also observed the participants as they told them to perform an action, and then stop. Individuals with higher levels of impulsivity make more mistakes and have delayed stopping times, the researchers explained.

"If a person's tendency to be impulsive increases, they tend to make snap decisions and the error rate increases," lead researcher Janelle van Wel from Maastricht University said in a statement.

Finally, tests assessing critical thinking skills, divided attention challenges and aspects of executive function and planning were included.

While both marijuana and cocaine increased impulsive responding, they did so in different ways: Marijuana made subjects slower and commit more errors, while cocaine influenced individuals to react more quickly and make more errors when told to control their impulses.

"This increased impulsivity after drug use could increase the likelihood of developing addiction," van Wel said.

Overall, the study suggested that long-term users of cocaine and marijuana were more impulsive when given either of the drugs than when given a placebo. However, the researchers also found that regular marijuana users experienced a roughly two to three times reduction in the magnitude of impairments in two of the tests when compared to occasional users.

In addiction, the relationship between the frontal cortex, which controls decision making, and the limbic system, which organizes emotional responses and memory, is affected. The study results suggest that marijuana decreases the frontal cortex's amount of control over behavior. Cocaine, in contrast, may increase impulsive responses from the limbic system.

"Both of these options would cause the decrease in impulse control we see in our study," van Wel said, noting that future studies are needed to prove whether or not this is the case.