Preclinical studies have shown that cannabinoid receptors and their ligands regulate bone metabolism but the clinical significance is unclear. Here we investigated the effects of recreational cannabis use on bone health in the Muirhouse study based in a socially deprived area in the North of Edinburgh. We recruited 263 subjects from the local community through advertisements. Bone density and fat mass were measured on a Hologic QDR4500 densitometer and relevant clinical variables were recorded. Of the 263 individuals recruited 163 (61.9%) were regular cannabis users with a median lifetime use of 20 805 joints (range 4197 100). The average age of participants was 44±10.3 years and 58% of subjects were female. We divided the population into three groups based on lifetime amount of cannabis taken; none (n=102); light users (420 800 joints; n=81) and heavy users (21 000197 100 joints; n=79). Heavy cannabis users were younger than controls (41.3±1.0 vs 49.6±0.9 years; P<0.001), had a higher dietary calcium intake (1368±104 vs 884±45 mg/day; P<0.001); a lower BMI (25.5±0.6 vs 29.3±0.7; P<0.001) and lower fat mass (27.0±9.5 vs 33.8±8.6; P<0.001). The data for moderate cannabis users were intermediate between heavy users and controls (data not shown). Heavy users were significantly more likely to use other illicit drugs (65.8% vs 2.9% for controls; P<0.001). There was no difference in BMD values between cannabis users and controls after adjustment for age, BMI, gender and other relevant variables. Fractures were more common in cannabis users (58% vs 46%; P=0.06), and multiple fractures were significantly more common (10.6% vs 1.9%, P−0.008). Heavy cannabis use is associated with reduced fat mass and an increased risk of fracture, but is not associated with BMD. The differences between mice and men may be due to the complex nature of cannabis, which contains not only THC, a CB1 agonist, but multiple other cannabinoids.
Disclosure: The authors declared no competing interests. This work was supported by Arthritis Research UK.