Female cannabis users have smaller volume of the cerebellum and poorer sleep quality, study finds

An analysis of data from the Human Connectome project indicates that chronic cannabis use in females, but not in males, is associated with a reduced volume in the cerebellum region of the brain and diminished sleep quality. This reduced sleep quality was more pronounced in females who began using cannabis at a younger age. The study was published in Frontiers in Psychiatry.

Cannabis, often referred to as marijuana or weed, is a plant that contains a group of compounds known as cannabinoids. The most notable and psychoactive of these is delta-9-tetrahydrocannabinol (THC), which induces the “high” sensation linked with cannabis consumption. Cannabis is consumed in various forms, including smoking, vaporizing, or consuming edibles. While considered an illicit drug in many parts of the world, it has been legalized in some regions and countries.

Prolonged use of cannabis is associated with impaired cognitive function, particularly in areas of memory, attention, and learning. It can also lead to addiction in some individuals, with withdrawal symptoms such as irritability and sleep disturbances when not using the drug.

Long-term cannabis use may increase the risk of mental health issues, including anxiety, depression, and psychosis, especially in individuals with a predisposition to such conditions. Additionally, chronic use can have adverse effects on lung health, similar to the effects of smoking tobacco, due to inhaling the smoke from cannabis joints or pipes.

There are notable gender differences in the short and long-term impacts of drug misuse. Research shows that substances, including alcohol, generally have more pronounced effects on females than males. Regarding cannabis, women, on average, transition more quickly from initial use to seeking treatment for cannabis use disorder than men do. While cannabis use and its associated disorders are more prevalent in men, the gap has been diminishing in recent years.

Study author Katherine L. McPherson and her colleagues noted that various studies suggested that there might be pronounced differences between women and men in the effects of chronic cannabis use on volumes of certain brain regions and the quality of sleep. They wanted to investigate whether this is indeed the case. To do that, they analyzed data from the Human Connectome Project.

They hypothesized that the brains of female cannabis users would show reduced volumes in areas dense with cannabinoid receptor type 1 – the structures in nerve cells responsive to cannabinoids, especially the THC in cannabis. The interaction of THC with these receptors in the brain generates the psychoactive effects or the “high” that users experience. These brain areas include the amygdala, hippocampus, and cerebellum. The researchers also postulated that female cannabis users would report worse sleep quality than their male counterparts.

From the Human Connectome Project database, which contains neuroimaging results of its participants, the researchers identified 170 individuals diagnosed with cannabis use disorder or those who had consumed cannabis more than 100 times in their life without being dependent on alcohol. They also chose a comparable group of 170 individuals who had used cannabis fewer than 10 times. This control group was matched based on age, gender, education, body mass index, race, and previous alcohol consumption to the group of cannabis users.

The researchers assessed and compared the functional magnetic resonance imaging data of these participants, along with their self-reported sleep quality using the Pittsburgh Sleep Quality Index.

Results showed that female, but not male, chronic cannabis users tended to have smaller volumes of the cerebellum region of the brain compared to non-users. The volume of the amygdala region of the brain was smaller in cannabis users than in non-users, regardless of sex. There were no differences in any of the other studied regions of the brain when researchers controlled for tobacco use.

Female chronic cannabis users tended to have poorer sleep quality compared to participants not using cannabis. Sleep quality was not associated with the volume of the cerebellum among female users of cannabis. However, sleep quality was even poorer in female cannabis users who started using cannabis at an earlier age. This was not the case with male cannabis users.

“These data corroborate prior findings that females may be more sensitive to the neural and behavioral effects of chronic cannabis use than males,” the study authors concluded.

The study makes a valuable contribution to the understanding of psychological and neural specificities of cannabis users. However, it is important to note that the design of this study does not allow any cause-and-effect conclusions to be drawn from the results. Additionally, lower volume in a brain region does not inherently imply a deficit or dysfunction; it may simply represent natural variability in brain anatomy among individuals or groups.

The study, “Cannabis Affects Cerebellar Volume and Sleep Differently in Men and Women”, was authored by Katherine L. McPherson, Dardo G. Tomasi, Gene-Jack Wang, Peter Manza, and Nora D. Volkow.