The popular notion may hold true: marijuana can cause laziness. This is the conclusion of a new study by researchers from the University of British Columbia in Canada, who found the primary active compound in marijuana – tetrahydrocannabinol – made rats less willing to attempt a cognitively challenging task.

Share on Pinterest The new study suggests marijuana use could lead to cognitive laziness.

Lead study author Mason Silveira, of the Department of Psychology at Columbia, and colleagues report their findings in the Journal of Psychiatry and Neuroscience.

According to the National Institute on Drug Abuse (NIDA), marijuana is the most commonly used illicit drug in the United States; a 2014 survey found more than 22 million Americans reported using the drug in the past month.

However, as of June 2016, 25 U.S. states and Washington, D.C., have legalized marijuana for medical or recreational use, and more states are expected to follow suit. This highlights the need to gain a better understanding of the risks and benefits marijuana use may pose.

A sense of euphoria, increased appetite, heightened sensory perception, hallucinations and delusions, and fear and anxiety are some of the well-known effects of marijuana use. Such effects are primarily down to the two main active compounds – known as cannabinoids – in the drug: tetrahydrocannabinol (THC) and cannabidiol (CBD).

There is a common belief that marijuana use can also affect a person’s motivation, making them lazy, though there has been little scientific evidence to support this association.

Silveira and colleagues note that previous studies have suggested the activation of cannabinoid receptors – which occurs through marijuana use – can affect decision-making related to physical effort, making a person physically lazy.

It is unclear, however, whether decision-making related to cognitive effort is affected in the same way. Silveira and colleagues wanted to find out.