(CNN) — Higher concentrations of tetrahydrocannabinol, or THC, the part of the marijuana plant that makes you feel high, are causing more people to become addicted in many parts of the world, according to a new review of studies.
Compared to people who use lower-potency products (typically 5 to 10 milligrams per gram of THC), those who use higher-potency cannabis are more likely to experience addiction and mental health consequences, according to the study released Monday. in academic journal Lancet Psychiatry.
Scientists established a “standard THC unit” of 5 milligrams of THC for research. That amount is said to produce mild intoxication for non-regular users.
“One of the highest-quality studies included in our publication found that high-potency, compared to low-potency, cannabis use was associated with a fourfold increased risk of addiction,” said study co-author Tom Freeman, Senior Lecturer in the Department of Psychology and Director of the Mental Health and Addiction Group at the University of Bath, UK, in an email.
In the United States, about 3 in 10 people who use marijuana have a cannabis use disorder, the medical term for marijuana addiction, according to the US Centers for Disease and Prevention (CDC).
The European Monitoring Center for Drugs and Drug Addiction (EMCDDA) found a 76% increase in people entering treatment for cannabis addiction in the past decade, “while cannabis potency continued to increase over the same period,” Freeman noted.
Furthermore, “a United Nations report revealed that in the last two decades, the proportion of people seeking treatment for cannabis addiction has increased in all regions of the world except Africa,” he said.
An annual increase in power
In one gram of cannabis herb, the dried and harvested tops of female marijuana plants that are commonly smoked, THC concentrations increase by about 2.9 milligrams each year, according to a study conducted in 2020 by Freeman and his team at the University of Bath.
In cannabis resin, the sticky brown plant sap from which extracts and concentrates are made, THC levels increased by about 5.7 milligrams each year from 1975 to 2017, according to the study.
Concentrated products can reach extremely high levels of THC.
Experts fear that this annual increase in potency is not clear to consumers. Although a product label might tell a person the “precise potency” of THC in a store where marijuana is legally sold, “people who buy cannabis illegally may not be able to access reliable information about the potency of the product they’re using,” Freeman said.
“However, certain types of cannabis tend to be more potent than others: cannabis extracts tend to be more potent than the cannabis flower,” he added.
Although people try to adjust their use when the potency of their cannabis varies, “for example, by adding less cannabis to their joint or inhaling less deeply,” these efforts don’t quite work, Freeman said. This means that “higher potency products continue to deliver a higher dose of THC to consumers than lower potency products,” she said.
Mental health is affected
As marijuana became more potent, cases of marijuana-associated psychosis increased, according to the review. Psychosis is a “loss of contact with reality” that can be characterized by hearing voices and having delusions, Freeman said.
“The evidence linking cannabis potency to addiction and psychosis is very clear,” he said.
High-potency cannabis users appear to have a significantly increased chance of developing generalized anxiety disorder than those who smoke less intense types of marijuana, according to a 2020 study.
However, the new review of studies found a “more mixed” connection between increased marijuana potency and depression and anxiety, “meaning the impact is unclear for these other mental health outcomes,” Freeman said.