Although there’s a plethora of research on the concentration of cannabinoids in hair follicles for the purpose of accurate drug testing, not many scientists have investigated the direct effects of cannabis on hair growth.
There are even studies on how hair straighteners affect cannabinoid concentrations in the hair follicles of those who use cannabis — in which the researchers found that THC content decreased and CBN content increased in the majority of the samples after exposure to a straightener. But alas, there is little research on how cannabis consumption affects growth.
However, one journal review suggests that THC may inhibit hair growth while CBD may promote hair growth.
“The endocannabinoid system in the skin consists of three main components,” the review states. “Endocannabinoids, such as 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (anandamide; AEA), endocannabinoid receptors, and the enzymes responsible for endocannabinoid synthesis and breakdown.”
The review then suggests the ECS may play a role in maintaining skin homeostasis. Dysregulated skin may lead to various conditions, including acne, atopic dermatitis, skin pigmentation, hair loss, or excessive hair growth.
Thus, by maintaining homeostasis, the ECS could play a role in preventing such conditions.
“Endocannabinoids are synthesized in hair follicles, epidermis, and sebaceous glands and [are] released in particular amounts depending on the need to maintain normal physiological function,” the review explains. “They bind to various receptors, but two classic receptors — cannabinoid receptor type 1 and cannabinoid receptor type 2 [are] expressed in nearly all types of skin cells [and] play vital roles in their actions.”
The figure by Gupta & Talukder illustrates the different roles CB1 and CB2 receptors play in the integumentary system. The integumentary system is the outermost layer of your body, which includes your skin, hair, and nails.
Keratinocytes — the epidermal cells that produce keratin in hair and skin — have CB1, CB2, G-coupled-protein receptor 55, and Peroxisome proliferator-activated receptor-gamma. Interactions at these receptors decrease keratinocyte differentiation, proliferation, inflammation, and malignant growth while increasing the rate of apoptosis (cell death).
Sebaceous glands — oil-producing glands primarily located near hair follicles — have CB2 receptors that increase lipid synthesis and apoptosis.
Sensory nerves in the skin have CB1 and CB2 receptors that decrease sensations of pain and itching.
Hair follicles have CB1, CB2, and TRPV receptors that decrease hair growth and proliferation but increase apoptosis. These receptors within the hair follicles also increase catagen, which is the second cycle in the phase of hair growth.
For further context, there are three stages of hair growth:
- Anagen: growth. This phase lasts two to seven years.
- Catagen: involution/shrinkage/growth stops. This phase lasts two to four weeks.
- Telogen: resting prior to shedding. This phase lasts about three months.
Immune cells within the integumentary system have CB1, CB2, and TRPV receptors, which decrease inflammation and cytokine production (pro-inflammatory signaling molecules).
Blood vessels in the integumentary system have CB1 and CB2 receptors that decrease angiogenesis, which is the formation of new blood vessels.
Sweat glands also have CB1 and CB2 receptors, though the effects of these receptors within sweat glands are unknown.
Honing in on Hair Growth: Is CBD the Key?
Based on the figure above, activated CB1 receptors within hair follicles actually decreases hair growth. This would imply that using THC — which binds to and activates CB1 & CB2 receptors — would increase the catagen phase of hair growth. Growth stops during the catagen phase and involution begins.
However, unlike THC, CBD is a negative allosteric moderator of CB1 and CB2 receptors. Rather than activating CB1 and CB2, CBD reduces THC’s activation of CB1 and CB2 receptors.
Thereby, in theory, CBD may prevent premature hair follicle regression and positively affect hair growth. The authors of the review also suggest that CBD may promote the anagen (growth) phase of the hair cycle by differentiating dermal progenitor cells into new hair follicles.
Additionally, CBD is an agonist (activates/stimulates) TRPV1 and TRPV4 channels.
“The activation of TRPV1 negatively impacts hair growth, but excessive activation desensitizes the receptor and may indirectly help growing hairs,” the authors continue. “An ex vivo study found that high concentrations of CBD (10μm) activated TRPV4 receptors and significantly reduced hair shaft development and induced apoptosis. However, at a low concentration (0.1μm), it increased hair shaft elongation perhaps via adenosine receptors.”
The authors of the review also cited another study in which 35 participants with androgenic alopecia (male/female pattern hair baldness) applied CBD-rich hemp oil to their scalp once a day for six months.
The oil increased the non-vellus (non-”peach fuzz”) hair count by 93.5%, and the males in the study had slightly better results than the females. Neither group reported any side effects from applying the oil, either.
Additional Factors & Considerations: Hormones & Nutrients
In addition to the presence of ECS receptors throughout the integumentary system, it’s also important to consider the effects of cannabis on other factors that impact hair growth. These other factors include hormones and nutrients.
Hormonal Considerations For Hair Growth
Estrogens, androgens, prolactin, thyroid hormone, growth hormone, melanin, and cortisol are all hormones involved in regulating hair growth. Hormone production and homeostasis are regulated by the endocrine system, which also possesses CB1 receptors.
CB1 receptors have been identified in the following parts of the endocrine system:
- Pituitary gland cells: In addition to the CB1 receptors in pituitary gland cells, it has been observed that these cells can also produce endocannabinoids.
- Thyroid glands
- Adrenal glands
- Vagus nerve endings
The ECS receptors throughout the endocrine system help regulate the secretion of prolactin, growth hormone, thyroid hormone, thyrotropin, oestradiol, and progesterone.
There are also sex differences in how cannabis affects male and female hormones. For example, cannabinoids appear to decrease testosterone in men and increase testosterone in women.
Thus, there is the possibility that cannabis use may indirectly affect hair growth — not just through CB1/CB2 interactions at the site of the hair follicle, but through indirect factors such as the influence of cannabis on hormone secretion.
Nutritional Considerations For Hair Growth
Good nutrition is a vital step toward healthy hair growth. Oftentimes, beauty magazines and gurus online discuss different “diets” or supplements that purportedly increase hair growth.
The key nutrients involved in regulating hair growth include:
- Water: Moisturizes hair
- Iron: Carries more oxygen to the hair, promoting growth
- Vitamin A: Acts as an antioxidant; reduces free radicals and inflammation that could negatively affect hair growth
- B vitamins (B7, B5, and B12): Promotes hair thickness and shine
- Vitamin D: Plays an important role in the hair follicle cycle
- Vitamin C: Promotes hair growth and strengthening; also absorbs iron
- Vitamin E: Strengthens and volumizes hair; increases circulation
- Silica: Strengthens hair
- Copper: “Essential for health of hair: needed to produce antioxidant superoxide dismutase”
- Selenium: Vital for maintaining scalp health
- Potassium: Maintains hair pH and moisture
- Magnesium: Vital for strong, healthy hair growth
- Omega-3 fatty acids: Helps prevent inflammation and promotes hair growth
- Calcium: “A key component of hair growth”
Hemp is nutrient-rich and contains several of these vital hair-healthy nutrients. Sprouted hemp seed powder is notably rich in vitamin B5, copper, and omega-3 fatty acids.
Thus, consuming hemp — either in the form of a seed, sprout, or sprouted hemp seed powder — could also positively affect hair growth.
Key Takeaways: CBD May Promote Hair Growth, But More Research is Needed
While there is a plethora of research on how to accurately determine THC concentrations within the hair of cannabis users, there is very little research on how cannabinoids actually affect hair growth.
However, the research thus far has identified ECS receptors throughout the integumentary system that may impact hair growth. Specifically, keratinocytes, sebaceous glands, and hair follicles of ECS receptors that — when agonized or antagonized — may affect the three stages of the hair growth cycle.
Activation of CB1 receptors in hair follicles increases the catagen phase of the hair cycle, thereby inhibiting hair growth. But CBD is an antagonist of CB1 receptors, meaning it blocks the activation of CB1. Therefore, it’s possible CBD may increase hair growth while THC may decrease it.
Furthermore, there are other mechanisms by which cannabinoids may indirectly affect hair growth. Such factors include the impacts of cannabis on the endocrine system (hormones) and the nutrient contents of hemp seeds and sprouts.
But as always, more large-scale clinical trials are needed in order to say definitively what the effects of cannabis use are on hair growth.
- Ettlinger, J., & Yegles, M. (2016). Influence of thermal hair straightening on cannabis and cocaine content in hair. Forensic Science International, 265, 13–16. https://doi.org/10.1016/j.forsciint.2016.01.002
- Gupta, A. K., & Talukder, M. (2021). Cannabinoids for skin diseases and hair regrowth. Journal of Cosmetic Dermatology, 20(9), 2703–2711. https://doi.org/10.1111/jocd.14352
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- Park, A. M., Khan, S., & Rawnsley, J. (2018). Hair Biology. Facial Plastic Surgery Clinics of North America, 26(4), 415–424. https://doi.org/10.1016/j.fsc.2018.06.003
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