Cannabis use is a frequently-discussed subject, not just in the realm of so-called alternative medicine (SCAM). In general, SCAM advocates view it as an herbal medicine and recommend it for all sorts of conditions. They also often downplay the risks associated with cannabis use. Yet, these risks might be substantial.
Cannabis potency, defined as the concentration of Δ9-tetrahydrocannabinol (THC), has increased internationally, which could increase the risk of adverse health outcomes for cannabis users. The first systematic review of the association of cannabis potency with mental health and addiction was recently published in ‘The Lancet Psychiatry’.
The authors searched Embase, PsycINFO, and MEDLINE (from database inception to Jan 14, 2021). Included studies were observational studies of human participants comparing the association of high-potency cannabis (products with a higher concentration of THC) and low-potency cannabis (products with a lower concentration of THC), as defined by the studies included, with depression, anxiety, psychosis, or cannabis use disorder (CUD).
Of 4171 articles screened, 20 met the eligibility criteria:
- eight studies focused on psychosis,
- eight on anxiety,
- seven on depression,
- and six on CUD.
Overall, higher potency cannabis, relative to lower potency cannabis, was associated with an increased risk of psychosis and CUD. Evidence varied for depression and anxiety. The association of cannabis potency with CUD and psychosis highlights its relevance in healthcare settings, and for public health guidelines and policies on cannabis sales.
The authors concluded that standardisation of exposure measures and longitudinal designs are needed to strengthen the evidence of this association.
The fact that cannabis use increases the risk of psychosis has long been general knowledge. The notion that the risk increases with increased potency of cannabis seems entirely logical and is further supported by this systematic review. Perhaps it is time to educate the public and make cannabis users more aware of these risks, and perhaps it is time that SCAM proponents negate the harm cannabis can do.