Adverse effects of heavy cannabis use: even plants can harm the brain

Research output: Contribution to journalArticlepeer-review


The spread of laws legalising cannabis for medicinal orrecreational use has been accompanied by more relaxedattitudes towards cannabis. Data from the United Statesshow that in states that have legalised cannabis, prevalenceof daily, weekly, and monthly cannabis use was 11.3%,18.3%, and 25.0% respectively, whereas in countries where itis still illegal, it was lower (7.4%, 11.6%, and 16.8%respectively). Evidence indicates a trend of increase amongadolescents, a particular vulnerable category for the initiationof substance use. In parallel, we have seen theconcentration of THC (D-9-tetrahydrocannabinol) in thecannabis sold both in the United States and in Europe risingand those types of cannabis with high THC, and a correspondingdecrease of cannabidiol (CBD) content,becoming more widely available. Most commonly, cannabisis used for its enjoyable effects, the “high” feeling. Inaddition, in those countries where its use has been legalised,many people smoke cannabis for medical use, anxiety,depression, and pain relief, with those suffering fromchronic pain being at higher risk of developing cannabis usedisorder (CUD).This review aims to challenge the widespread view thatcannabis being a “plant” does not carry adverse effects, andreview the evidence concerning the effects of cannabis use onmental health and cognition
Original languageEnglish
Pages (from-to)1-8
Number of pages8
Publication statusPublished - 2020


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