Cannabis & bones: CB2, osteoporosis & bone healing

The endocannabinoid system in bone metabolism

Bones are living tissues that are constantly being remodeled – by osteoblasts (bone formation) and osteoclasts (bone resorption). The endocannabinoid system directly regulates this remodeling: CB1 and CB2 are expressed by both cell types, and endocannabinoids are important modulators of bone physiology.

CB2 receptors are the dominant cannabinoid receptor class in bone – which means that cannabinoids without a psychoactive CB1 effect (such as CBD, CBG, beta-caryophyllene) can act on bone.

CB1 and CB2 in bone: Different functions

Study situation: cannabinoids and bone density

Idris et al. 2005 (Nat Med): CB2 knockout mice developed age-related osteoporosis faster and more severely than wild-type mice. CB2 activation protects against osteoporotic bone loss. Conversely, CB2-selective agonists increased bone density in animal models.

Idris et al. 2009 (Bone): CB2 agonist JWH-133 prevented ovariectomy-induced osteoporosis in mice. Mechanism: Inhibition of osteoclastogenesis via RANKL suppression.

Ofek et al. 2006 (PNAS): Anandamide and CB2 activation inhibit osteoclastogenesis and promote osteoblast activity in vitro. CB2 could be a therapeutic target for osteoporosis.

Cannabis and fracture healing – Koren et al. 2019 (J Bone Miner Res): CBD significantly accelerated bone healing in rat fracture model. Bones in the CBD group had higher bending stiffness and better mineralization after 8 weeks.

Clinical implications: Osteoporosis and cannabis

Osteoporosis affects 6 million people in Germany – mainly postmenopausal women and older men. Paradoxically, THC could have a bone-degrading effect on osteoclasts through CB1 activation:

Muniyappa et al. 2013 (Bone): Survey study: Chronic cannabis users had lower bone density in some cohorts. But confounders (nicotine, alcohol, BMI) difficult to control.

Conclusion for practice: CBD (without THC): potentially bone-protective via CB2. THC with high chronic consumption: possible risk of osteoporosis through CB1 on osteoclasts. No clinical use of cannabis as osteoporosis therapy at present.

FAQ: Cannabis and bones

Summary

CB2 receptors in bone regulate osteoblasts and osteoclasts. CB2 activation has a bone-anabolic effect and inhibits resorption – strongly supported by preclinical evidence (Idris 2005, 2009). CBD promotes fracture healing in animal models (Koren 2019). Chronic THC associated with lower bone density in some studies. Clinical human studies are lacking for direct therapeutic use. CB2 immune system guide for further CB2 knowledge; cannabis in rheumatism for related joint diseases.