High-Potency Cannabis Use Linked with Mental Health Issues

The University of Bristol recently completed the first longitudinal study on high-potency cannabis and its effects on mental health. Here's what they found.

We note that the subject contained in this article represents illegal activity in certain jurisdictions. Whilst we do not condone any acts which are contrary to any such laws, we understand that readers in those jurisdictions which have decriminalised cannabis may find this article of interest.

Is there a connection between mental health issues and cannabis use? Are conditions like depression, anxiety and substance abuse more common in those who consume higher potency weed? We've just discovered that a higher THC potency doesn't mean a higher high, but can it have more serious implications?

In the first general population study of its kind, researchers at the University of Bristol interviewed 1087 UK residents at the age of 24 to understand the link, if any, between cannabis potency and increased likelihood of mental health conditions. So, what's the link between high potency cannabis and mental health disorders?

What did the study find?

Cannabis has long been linked to negative mental health outcomes, and this study suggests that there is an association between high potency cannabis use and mental health conditions. In particular, anxiety and addiction.

The researchers presented the study subjects with a range of questionnaires to understand their current and past cannabis, alcohol, nicotine and illicit drug usage.

The subjects of the study were from the Avon Longitudinal Study of Parents and Children (ALSPAC) group. All adolescents still registered in the ALSPAC program were contacted to opt in to this study.

The questionnaire given at age 24 asked subjects what type of cannabis they have consumed in the past 12 months and the frequency of their cannabis use in that time. Interestingly, the answer choices for both questions were quite restrictive.

For type of cannabis, the options available were "herbal cannabis/marijuana," "skunk/other stronger types of herbal cannabis," "hashish/resin/solid," "other," or "don't know." Recreational marijuana is not legal in the UK, so exact levels of THC potency would rarely be known to consumers. This limitation was acknowledged by the research team in their report.

When asking frequency of use in the past 12 months, the researchers dichotomised the answers to "monthly or less," or "weekly/daily use."

The research team used a number of external standardized tests to understand the subjects' reliance on various substances and identify any substance abuse issues they may have. These included the Cannabis Abuse Screening Test, the Fagerstrom Test for Nicotine Dependence and the DMS-5 criteria for alcohol use disorder.

Of the 1087, 141 subjects reported high-potency cannabis use, and 946 reported low-potency use. These two groups were then compared and analysed for their mental health and substance abuse issues.

The differences between the two groups is quite distinct. More than half of the high-potency group regularly used cannabis, whereas in the lower-potency group, it was under 20%. More than 10% of the high-potency group reported cannabis abuse problems, compared to under 1% in the low-potency group.

High-potency users were more likely than their low-potency counterparts to use other illicit drugs and have alcohol use disorder. 37% of high-potency users had a tobacco dependence, compared with just over 15% of the lower-potency group.

Major depression, showing moderate or severe symptoms, was slightly higher in the high-potency group but generalized anxiety was almost double within the high-potency users.

High-potency users were also almost twice as likely to report frequent or distressing psychotic-like episodes, but this association was considered weaker when taking frequency of cannabis use into account.

Overall, higher-potency users were more likely to report having experienced problems associated with their cannabis use, and more likely to concurrently be using other illicit drugs, have a tobacco dependence, alcohol use disorder, generalized anxiety disorder, and psychotic episodes.

What does this mean for cannabis use and legalization?

As mentioned previously, cannabis use in the UK is illegal. This means there is no regulation of cannabis types or potency and reliable information can't be provided to consumers when purchasing.

The serious mental health implications found in this study present an evidence-based reason for legalization and regulation of cannabis products.

Providing public health messaging regarding the importance of reducing both the frequency of cannabis use and the potency of the drug, as well as limiting the availability of high-potency cannabis, may be effective for reducing the harms associated with cannabis use.

In addition to positive mental health outcomes, understanding the link found in this study is important for policy making practices, including taxation and potential limits on cannabis potency.

The findings of this study highlight a link between lower socioeconomic status and earlier exposure to cannabis use, which is more likely to lead to high-potency cannabis consumption, substance abuse issues in late adolescence and early adulthood and mental health disorders. By forming cannabis policy with concentration limits, governments would be playing their role in allowing adults to make informed decisions with reduced health risks.

As was recently discovered, higher potency cannabis does not result in a higher 'high', and so there is seemingly little or no benefit to consuming higher potency cannabis. This study shows that there can be severe disadvantages in higher potency cannabis, making a strong argument for restricting potency in legally sold cannabis.

What's next?

In many ways, this study presents a chicken-egg discussion. Do depressed people smoke higher potency weed? Or does higher potency weed give people depression?

Many of the subjects who reported higher-potency use were males from lower socio-economic status families, and were exposed to cannabis earlier than lower-potency users.

This crossover with early exposure and substance abuse outcomes indicates there may be similar risk factors between developing mental health disorders and substance abuse, and the selection of higher-potency cannabis.

Study on these links is very limited, and the researchers have suggested that "further consideration of the role of cannabis potency in the causal path to mental health disorders is warranted."

As states and countries around the world continue to legalize recreational cannabis use, studies like these need to continue so adults can make informed decisions about the effects of cannabis, the potency and the method of consuming.

An illegal cannabis market unfortunately does not give consumers the information necessary to make these informed decisions, and puts users at risk.

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Laura Desmond
Laura Desmond

Laura Desmond is an Adelaide-based writer with a keen interest in the arts, gender politics and social change. She is currently working to obtain a Master in Writing through Swinburne University.

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