Marijuana’s Effects on the Brain

Source: "How Cannabis Affects Our Cognition and Psychology," Neuroscience News, 13 May 2022.

• "... the main users are adolescents and young adults, whose brains are still in development. They may therefore be particularly vulnerable to the effects of cannabis use on the brain in the longer term."
• "We showed that participants with the condition had significantly worse performance on memory tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) compared to the controls, who had either never or very rarely used cannabis. It also negatively affected their “executive functions”, which are mental processes including flexible thinking. This effect seemed to be linked to the age at which people started taking the drug – the younger they were, the more impaired their executive functioning was."
• "Cognitive impairments have been noted in mild cannabis users as well. Such users tend to make riskier decisions than others and have more problems with planning."
• "We showed that, while male cannabis users had poorer memory for visually recognizing things, female users had more problems with attention and executive functions."
• "... some previous research has suggested that reward and motivation – along with the brain circuits involved in these processes – can be disrupted when we use cannabis. This may affect our performance at school or work as it can make us feel less motivated to work hard, and less rewarded when we do well."
• "We have shown that it is related to higher “anhedonia” – an inability to feel pleasure – in adolescents."
• "Assessing 2,437 adolescents and young adults (14-24 years), the authors reported a six percentage points increased risk – from 15% to 21% – of psychotic symptoms in cannabis users without a predisposition for psychosis. But there was a 26-point increase in risk – from 25% to 51% – of psychotic symptoms in cannabis users with a predisposition for psychosis."
• "Cognitive and psychological effects of cannabis use are ultimately likely to depend to some extent on dosage (frequency, duration, and strength), sex, genetic vulnerabilities, and age of onset. But we need to determine whether these effects are temporary or permanent. One article summarising many studies has suggested that with mild cannabis use, the effects may weaken after periods of abstinence. But even if that’s the case, it is clearly worth considering the effects that prolonged cannabis use can have on our minds – particularly for young people whose brains are still developing."