A new review of studies in the journal Lancet Psychiatry suggests that marijuana is gradually becoming more potent and more addictive.
Review coauthor Tom Freeman, a professor at Britain’s University of Bath, told CNN that “use of high-potency cannabis, compared to low-potency cannabis, was linked to a four-fold increased risk of addiction.” He noted that marijuana addiction rates have risen in all regions except Africa.
Over time, new strains of marijuana have been bred to have higher concentrations of tetrahydrocannabinol (THC), the chemical that gives users a high.
Scientists have established a standard unit of 5 milligrams to measure THC. A 2020 study by Mr. Freeman showed that the concentration of THC in cannabis flower rises 2.7 milligrams per gram every year, as reported by CNN.
In cannabis resin, THC potency has increased by 5.7 milligrams per gram every year from 1975 to 2017, according to the 2020 study. Resin is used for extracts and concentrates used in processed weed products.
Consumers, however, may not be aware of this gradual growth in potency. Mr. Freeman told CNN that “people buying cannabis illegally may not be able to access reliable information about the potency of the product they are using.”
In a University of Bath press release, review lead author Kat Petrilli was quoted as saying that “people who use higher potency cannabis could be at increased risks of addiction as well as psychosis.”
The connection between marijuana and depression and anxiety remains unclear, according to the review of studies.