Researchers from the University of Bath used donated cannabis to produce accurate results in a study conducted to test the hypothesis that users of high-strength cannabis would experience more anxiety, depression and psychosis-like symptoms than users of lower-strength cannabis.
Previous studies have found associations between the use of high-strength cannabis and an increased risk of psychosis and cannabis use disorder. One case-control study found the likelihood of a patient receiving a psychosis diagnosis to be three times higher in those that used high-strength cannabis than in those that didn’t.
Researchers realised there was a common flaw in previous studies that involved the self-reporting of cannabis strength by participants. The study authors explained that “While there is evidence to suggest high potency cannabis could be associated with poorer mental health outcomes and problematic cannabis use, these studies carry limitations in the measure of exposure.”
The majority of previous studies record the potency of cannabis based on the reports of participants. However, self-report measures of cannabis potency only provide an approximation, instead of an accurate record of the amount of THC. This can lead to bias or measurement error in the study results.
By measuring the THC concentration of the cannabis actually used by participants, researchers were able to accurately understand the real potency of the cannabis consumed.
A total of 410 participants were involved in the study, aged between 16 to 24 years old, and had all been using cannabis at least once a month for at least a year. Inclusivity criteria meant participants were not to have any diagnoses for psychosis and no learning impairments. Of the 410 participants,194 were daily cannabis users, and 216 reportedly used cannabis less frequently.
“Participants were tested on two separate days, in their own homes. They were tested once when acutely intoxicated with their own cannabis and once when non-intoxicated. On the intoxicated test day, participants provided a sample of 0.3 g of the cannabis they were about to smoke. Only outcome data of the non-intoxicated condition was used for this analysis,” researchers explained.
The results showed that 39% of participants were more fond of high-strength cannabis, as opposed to lower strength. The average level of THC in cannabis donated by those who preferred high-strength cannabis was 8.95%, whereas the level of THC in samples of those who preferred lower-strength was 7.90%.
When analysed to examine if there was a link between high-strength cannabis use and mental health conditions, the results showed that “Preference for high potency cannabis use, compared to low potency cannabis use, was associated with a slight increase in cannabis dependence.
“The increased risk of cannabis dependence in users of cannabis that preferred high potency types remained unchanged after adjusting for age, sex, alcohol use, tobacco use and other illicit drug use.
“However, after additional adjustments for cannabis use frequency, there was only weak evidence for a very small effect of cannabis potency preference on cannabis dependence.
“Frequency of cannabis use was associated with a slight increase in risk of cannabis dependence.”
In their conclusion, researchers explained, “Participants who preferred high potency cannabis might be at increased risk of problematic cannabis use. However, these effects were not supported by triangulation with measures of THC concentration in cannabis. High potency cannabis preference and THC concentration might be associated with symptoms of depression but more evidence is needed to understand this relationship. High-potency cannabis use, compared to low-potency cannabis use, was not associated with psychosis-like symptoms and we found only weak evidence for a small association between THC concentration and symptoms of anxiety. These findings highlight the importance of improving the methodology used to assess cannabis use in research and clinical settings.”