Cannabis, a popular drug used by humans for thousands of years, has become legal to prescribe or take in many countries due to its effects such as feelings of joy and relaxation. However, recent studies published in The Journal of Psychopharmacology, Neuropsychopharmacology, and the International Journal of Neuropsychopharmacology show that the drug can influence various cognitive and psychological processes.
Tetrahydrocannabinol (THC), the main psychoactive compound in cannabis, acts on the brain’s “endocannabinoid system”, which are receptors that respond to the chemical components of cannabis. These receptors are densely populated in prefrontal and limbic areas in the brain, which are involved in reward and motivation.
Cannabis use can affect cognition, especially in those with cannabis-use disorder characterized by persistent desire to use the drug and disruptions to daily activities like work or education. Participants with this condition were shown to have significantly worse performance on memory tests compared to those who had never or very rarely used cannabis. Cannabis use also negatively affects executive functions, which are mental processes including flexible thinking. The younger people start taking the drug, the more impaired their executive functioning may be.
Although most studies have been conducted in males, there has been evidence of sex differences in the effects of cannabis use on cognition. While male cannabis users had poorer memory for visually recognizing things, female users had more problems with attention and executive functions.
Cannabis use can also affect how we feel. Cannabis can make us feel less motivated to work hard and less rewarded when we do well. It is related to higher “anhedonia” – an inability to feel pleasure – particularly pronounced during lockdowns such as those during COVID-19 pandemic.
Cannabis use during adolescence has been reported as a risk factor for developing psychotic experiences as well as schizophrenia. Cannabis use moderately increases the risk of psychotic symptoms in young people but has a much stronger effect in those with a predisposition for psychosis. Studies have suggested that dopamine and glutamate may be important in the neurobiology of these conditions.
Cognitive and psychological effects of cannabis use are likely to depend on dosage, sex, genetic vulnerabilities, and age of onset. However, it is worth considering the effects that prolonged cannabis use can have on our minds particularly for young people whose brains are still developing. It remains to be determined whether these effects are temporary or permanent.