A new study, funded by the US National Institute on Drug Abuse, found no association between long-term medical cannabis use and changes in brain function related to memory, reward or self-control.
The study is thought to be among the first to examine long-term brain differences among patients using cannabis for medical symptoms, compared to a control group.
As participants did not use cannabis heavily beforehand and were obtaining medical cannabis for the first time, the study was ‘uniquely positioned’ to examine the brain before and after they began to use cannabis regularly, a period which is usually ‘difficult to capture’, according to the researchers.
The findings, which were published in the journal JAMA Open Network, suggest that light to moderate use of cannabis for medical reasons may have little impact on brain function, even over the long term.
The team followed 57 participants seeking medical cannabis cards for anxiety, depression, pain, or insomnia symptoms, to establish whether there was an association between year-long medical cannabis treatment and brain activation during cognitive processes implicated in cannabis use.
Participants were aged between 18 and 65 years, with the majority identifying as female and white.
MRI scans were collected from participants at the beginning of the study and after one year of treatment with medical cannabis. These were then compared to those taken from a group of healthy controls.
According to the results, during working memory, reward, and inhibitory control tasks did not differ statistically from baseline to one year and were not associated with changes in cannabis use frequency.
“This suggests that cannabis use for medical purposes, within the snapshot of cognition captured by these tasks and within a mostly older, White, female, and generally well-educated population, did not have a significant association with brain activation or cognitive performance,” the authors state.
The study had a number of limitations which should be considered alongside the findings, including the limited number of participants and lack of diversity among demographics.
The authors recommend that further research is carried out in more diverse populations to understand how differences in product type, amounts, and patterns of use might affect the brain in cannabis users for medical symptoms.
However, they conclude: “Our results suggest that adults who use cannabis, generally with light to moderate use patterns, for symptoms of pain, anxiety, depression, or poor sleep, experience few significant long-term neural associations in these areas of cognition.”