Overview of disorders of cannabis use
Cannabis is derived from the cannabis plant in the form of dried leaves and flowers (cannabis plant material, also called marijuana), resin (hashish) and oil (hashish oil)1Australian Institute of Health and Welfare (AIHW). In Australia, cannabis is mainly smoked in cigarettes (joints) or in water pipes (bongs) or vaporised, although edible products are increasing in popularity. The main psychoactive ingredient is delta-9-tetrahydrocannabinol (THC), a partial agonist at cannabinoid receptors in the central nervous systemAlcohol and Drug Foundation (ADF), 2022.
Cannabis is one of the most widely and increasingly used psychoactive substances in Australia and the world. More than 1 in 3 Australian adults have used cannabis in their lifetime, and more than 1 in 10 have done so in the past 12 monthsAustralian Institute of Health and Welfare (AIHW). Many people also use other substances, especially tobacco; managing nicotine dependence is importantManning, 2018.
In the last 25 years, a wide variety of synthetic cannabinoid-receptor agonists (SCRAs), a form of novel psychoactive substance, has appeared on the illicit drug marketEuropean Monitoring Centre for Drugs and Drug Addiction (EMCDDA), 2022. Most SCRAs are full agonists at cannabinoid receptors, so are more potent than THC (a partial agonist) and have increased risk of harms, including cardiovascular effectsTait, 2016van Amsterdam, 2015. In contrast to the illicitly manufactured SCRAs, other synthetic cannabinoids (eg dronabinol and nabilone) have been approved overseas for therapeutic use. SCRAs, dronabinol and nabilone are expected to cause dependence similar to THC.
Prescribing advice for medicinal cannabinoids (synthetic or plant-derived) is outside the scope of these guidelines2.
Most people who use cannabis consume relatively small amounts without serious negative consequences, but even occasional use can cause harm. Cannabis effects and potential harms lists some common effects, including potential harms.
The risk of cannabis dependence is increased in people who start using at a young age and those who use frequently; 20 to 30% of people who use cannabis weekly develop dependence compared to 50% of people who use dailyZvolensky, 2020. Cannabis dependence can develop with medicinal use, but data on its prevalence are limitedGilman, 2022Nielsen, 2019.
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Short-term effects |
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mild euphoria, relaxation and disinhibition altered perception (eg time perception, heightened experiences) increased appetite nausea, headache, red sclerae elevated heart rate dizziness, impaired balance and coordination panic, confusion, paranoia can unmask undiagnosed mental illness impaired short-term memory and judgementBahji, 2020 risk of accidental injury (eg motor vehicle accidents)Zahra, 2020 |
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Long-term effects |
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cannabis dependence cannabinoid hyperemesis syndromeChocron, 2019 may increase risk of mental illness cognitive impairment (largely reversible on stopping) lower educational attainmentSilins, 2015 chronic bronchitis [NB1] may increase risk of oropharyngeal and some lung cancers cardiovascular damage [NB2] |
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Note:
NB1: Even in the absence of concurrent tobacco use, cannabis increases the risk of chronic bronchitis and may be a risk factor for oropharyngeal and some lung cancersNSW Health, 2008 Ribeiro, 2016 NB2: Cannabis can cause vasoconstriction, myocardial infarction and stroke, and may affect long-term myocardial functionAuger, 2020. |