Can cannabis affect the aging brain? A large-scale study recently published points to a surprising connection between cannabis use in older age and certain indicators of brain health and cognitive functioning.
The study was based on data from the British Biobank database and included 26,362 participants aged 40 to 77, with an average age of 55. The researchers examined the connection between cumulative lifetime cannabis use and the volume of different brain regions as well as performance on cognitive tests.
The main finding was that higher lifetime use was generally associated with larger volumes in certain brain regions and with better performance in areas such as learning, memory, processing speed, attention, and executive function. Unlike studies conducted among adolescents that raised concerns about harm to brain development, the current study focused on people aged 40 and older – a population in which some use cannabis for health reasons, such as coping with chronic pain or sleep difficulties.
The researchers focused especially on areas rich in cannabinoid receptors of the CB1 type, which are considered sensitive to the effects of cannabis. Among the areas examined was the hippocampus, a central region in memory and learning processes, known to tend to shrink with age and in conditions of dementia. The study found that among regular cannabis users larger volumes were recorded in this region compared to those who did not use it.
What is the meaning of larger brain volume?
When discussing the volume of brain regions, the reference is not to the size of the entire brain, but to the measurement of specific areas. With increasing age, a decrease in the volume of certain regions is sometimes observed due to processes of neural degeneration. This decrease is often associated with cognitive decline and an increased risk of dementia. In the current study it was found that in most of the regions examined there was a positive association between larger volume and better cognitive performance.
However, the picture is not unequivocal. In one brain region, called the “posterior cingulation”, it was found that higher use was actually associated with smaller volume. This region is involved in memory, learning, and emotional processing. The researchers note that there are studies indicating that smaller volume in this region may actually be associated with better working memory, and therefore the meaning of the finding is not entirely clear.
In an analysis according to levels of cannabis use, it was found that in many cases actually the moderate-use group showed the most positive results both in brain volume and in cognitive measures. In a small number of measures, such as the volume of the right amygdala and visual memory, the high-use group showed better results. The findings suggest the possibility of a dose-dependent effect, but the researchers emphasize that they did not have detailed data on product types, concentrations of active substances, or precise usage patterns.
The researchers also examined differences between men and women. Although no consistent and clear pattern was found favoring one sex over the other, significant interactions were identified in several brain regions and cognitive measures. It is possible that the differences stem from variation in the endocannabinoid system and from hormonal influences, but additional research on the subject is required to determine this.
According to the researchers, this is a period in which more and more adults are turning to cannabis for medical or functional reasons. At the same time, there are still no comprehensive controlled clinical trials that make it possible to establish unequivocal recommendations. The study does not constitute a recommendation to begin using cannabis to prevent dementia, but rather emphasizes that the connection between cannabis and brain health is complex and depends on age, patterns of use, and personal characteristics.
The main conclusion is that the effect of cannabis on the brain is not uniform throughout life. It is possible that at an older age different biological mechanisms exist from those in adolescence, but the picture is far from complete. For public health and policy makers, understanding the possible effects, both positive and negative, is especially important in an era of increasing availability and lively public discourse surrounding the use of psychoactive substances.