Study finds no link between high-THC cannabis and psychosis

Researchers have found little evidence of a link between high potency cannabis and an increased risk of psychosis and other mental health symptoms.

A team of researchers at the University of Bath have explored the association between cannabis potency and the likelihood of developing cannabis dependence and mental health issues including anxiety, depression and psychosis. 

Previous studies have linked cannabis potency and high-THC levels to an increased risk of mental health problems, including symptoms of psychosis. However, this is reported to be the first time a study has used multiple data sources and methods, including self-reporting and objective measures of cannabis potency, to understand its effects.

The researchers assessed the association between cannabis potency and mental health outcomes in 410 16-24-year-olds who had used cannabis at least once a month for a year. Just under half of participants were reported to be daily consumers.

Participants provided a 0.3g sample of the cannabis they were about to smoke and were tested in their own home on two separate occasions, once when intoxicated and once when non-intoxicated. 

The sample was tested for THC concentrations and the consumers were given a series of questionnaires and scales to respond to measuring potency preference, cannabis dependence, levels of anxiety and depression and psychosis-like symptoms. 

After adjusting for confounding factors, the researchers found no association between more potent cannabis and an increased risk of dependence or psychosis-like symptoms.

While a preference towards higher potency cannabis was associated with a ‘slight increased’ risk of cannabis dependence, this was not the case after adjusting for frequency of use.

They also report ‘weak evidence of a small association’ between cannabis potency and depression and anxiety. 

The authors state: “No association was found between THC concentration in cannabis and cannabis dependence. There was weak evidence of a small association between cannabis potency and depression and anxiety. There was no association between high potency cannabis preference or THC concentration in cannabis and psychosis-like symptoms… High potency cannabis preference and THC concentration might be associated with symptoms of depression but more evidence is needed to understand this relationship.”

Read the full study here 

Previous research

This research is the latest in a line recent studies which aim to shed more light on the relationship between cannabis and psychosis.

A study from earlier this year found ‘no significant association’ between any measure of cannabis use and the onset of psychosis, persistence of symptoms or functional outcomes. 

Meanwhile research from 2021 looked at the relationship between adolescent cannabis use and adult-onset psychosis in a longitudinal co-twin control analysis. The authors found no evidence that a greater consumption of cannabis was linked to a higher likelihood of developing psychosis in adulthood. 

Read more on the relationship between cannabis and psychosis here 

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