Cannabis

Key findings

  • Cannabis is the most widely used illicit drug in Australia.
  • Cannabis was the second most common drug type identified at toxicology for accidental deaths in 2016.
  • Cannabis use among the Australian general population remained stable between 2001 (12.9%) and 2016 (10.4%).
  • People who use cannabis are older than they were previously - the average age increasing from 29 in 2001 to 34 in 2016.
  • Cannabis is used more frequently than other illicit drugs, such as ecstasy (2%) and cocaine (3%), with 36% of recent users reporting weekly use.
  • There has been an increasing tolerance for regular adult cannabis use among the Australian general population - rising from 9.8% in 2013 to 14.5% in 2016.
  • In 2016, 85% of Australians favoured the use of cannabis for medicinal purposes, rising from 69% in 2013.

The two most common subspecies within the cannabis genus from which cannabis is harvested are Cannabis sativa and Cannabis indica. Cannabis comes in three main forms:

  • Herbal cannabis (also referred to marijuana) – the dried leaves and flowers of the cannabis plant (the weakest form);
  • Cannabis resin (hashish) – the dried resin from the cannabis plant;
  • Cannabis oil (hashish oil) – the oil extracted from the resin (the strongest form) [1,2].

Cannabis is most commonly smoked in a rolled cigarette (joint) or water pipe, often in combination with tobacco, but it may also be added to food and eaten. Cannabis oil is generally applied to cannabis herb or tobacco and smoked, or heated and the vapours inhaled [2].

The main psychoactive component of the cannabis plant is delta-9-tetrahydrocannabinol (THC). THC is highest in the flowering tops and leaves of the plant. Other than THC, cannabis has more than 70 unique chemicals that are collectively referred to as cannabinoids [2]. Cannabis is a central nervous system depressant, but also alters sensory perceptions and may produce hallucinogenic effects when large quantities are used [1,2]. The use of cannabis for medicinal purposes has also recently been legislated by the Australian parliament with a number of reviews complete or underway relating to its use.

Synthetic cannabis is a new psychoactive substance that was originally designed to mimic or produce similar effects to cannabis [3]. The availability, consumption and harms associated with synthetic cannabis are discussed further in the section on new (and emerging) psychoactive substances (NPS).

Availability

Cannabis is relatively easy to obtain in Australia. Regular injecting drug users and users of ecstasy or other stimulants report that cannabis is ‘easy’ or ‘very easy’ to obtain., This has remained stable over time, as has purity and pricing [4,5]. Perceived availability was the highest for hydroponic cannabis (88% of IDRS users and 84% of EDRS users rated it ‘easy’ or very easy’ to obtain), followed by bush cannabis (77% of IDRS users and 75% of EDRS users rated it ‘easy or very easy’ to obtain) [4,5]. The primary source of cannabis reported by recent users aged 14 years or older was friends, followed by dealers (66% in 2016) [6] (Table S2.5).

In 2016–17, the majority of the number of national illicit drug seizures (52.9%) and arrests (50.1%) were for cannabis [2]. However, cannabis only accounted for 27.5% of the weight of illicit drugs seized nationally. There was 77,549 national cannabis arrests in 2016–17, with the number of national cannabis arrests increasing nearly 50% over the last decade (52,465 in 2007–08) [2,7]. The number of national cannabis seizures has also increased over the decade, from 41,661 in 2007–08 to 60,006 in 2016–17, while the weight of cannabis seized nationally decreased, from 8,909.2 kilograms in 2007–08 to 7,547.8 kilograms in 2016–17 [2,7].

Widespread domestic cultivation generally makes the trafficking of herbal cannabis into Australia unnecessary and unprofitable [2].

Consumption

Cannabis continues to be the world’s most widely used illicit drug, with an annual prevalence of 3.8% of the adult population, or an estimated 183 million people (ranging between 128 to 238 million) having used cannabis in the past year [8].

The 2016 NDSHS showed that cannabis continues to have the highest reported prevalence of lifetime and recent consumption among the general population, compared with other illicit drugs (Tables S2.31 and S2.32).

  • For people aged 14 and over in Australia in 2016, 35% (or approximately 6.9 million) had used cannabis in their lifetime and 10.4% (or 2.1 million) used cannabis in the prior 12 months (Figure CANNABIS1).
  • Recent and lifetime use of cannabis has remained relatively stable over the past decade but there were some statistically significant changes among different age groups [6] (Tables S2.38 and S2.39).
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Cannabis use by age and sex

Since 2001, recent cannabis use has generally declined among the younger age groups (those aged 14–39), but has either increased or remained stable for the older age groups (40 or older).

  • Compared with those in other age groups, people in their 20s continue to be the most likely to use cannabis but this declined from 29% in 2001 to 22% in 2016.
  • Recent cannabis users were more likely to be male (13.4%) than female (8.3%) [6] (Table S2.39).

Between 2013 and 2016 there was a slight but significant increase among people aged 60 and older using cannabis (from 1.2% to 1.9%) (Figure CANNABIS1; Table S2.39).

  • In 2001, the average age of cannabis users was 29 and this increased to 34 in 2016. These results suggest there may be an ageing cohort of cannabis users.

Cannabis is used more frequently than other drugs such as ecstasy and cocaine. Specifically, 36% of people who used cannabis did so as often as weekly or more, compared with only 2% and 3% of ecstasy and cocaine users respectively. Males were more likely than females to use cannabis weekly (41% compared with 29%) [6].

The Australian Secondary Students’ Alcohol and Drug Survey (ASSAD) examines alcohol and other drugs use among students aged 12–17. Results showed that:

  • In 2014, cannabis was the most commonly used illicit substance by this cohort, with 16% of students reporting ever using cannabis and 7% using it in the month before the survey.
  • There were no significant differences in the proportion of students using cannabis in the past week, past month or lifetime between 2008 and 2014 or between 2011 and 2014 [9] (Table S2.40).

Further information about alcohol and other drug use by secondary school students.

Geographic trends

In 2016, recent cannabis use for persons aged 14 and over was highest in the Northern Territory (16%)—almost double the usage in the Australian Capital Territory (8.4%). However the proportion of recent cannabis use has remained stable between 2013 and 2016 for all states and territories (Table S2.33).

Australians living in Remote and Very Remote areas of were about 1.6 times more likely than those living in Major cities to have used cannabis in the previous 12 months (17% compared with 10.4%). Levels of recent use for people living in Inner and Outer Regional areas were consistent with those for people from Major Cities, at about 10%. Regardless of what socioeconomic area a person came from, about 1 in 10 had recently used cannabis (Figure CANNABIS2; Tables S2.12–S2.13).

The National Wastewater Drug Monitoring Program (NWDMP), measures the presence of substances in sewerage treatment plants across Australia. The most recent data indicates that the average consumption of cannabis in regional areas was almost double capital city consumption [18].

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Explore state and territory data on the use of cannabis in Australia.

Harms

The effects of cannabis (like all drugs) vary from one person to another including, but not limited to, the amount consumed, the mode of administration, the user’s previous experience, mood and body weight [1,10]. The active drug in cannabis makes its way into the bloodstream more quickly when cannabis is smoked, compared to when it is orally ingested. An overview of some of the short and long-term effects of cannabis are provided in Table CANNABIS1.

Table CANNABIS1: Effects of cannabis

Short-term effects

Long-term effects

  • Mild euphoria, relaxation and reduced inhibitions
  • Perceptual alterations, including time distortion and intensification of ordinary experiences
  • Feelings of hunger
  • Panic reactions, confusion and feelings of paranoia – mainly reported by na├»ve users
  • Nausea, headache and reddened eyes
  • Increased heart rate for up to three hours after smoking
  • Dizziness, with impaired balance and coordination
  • Physical dependence
  • Upper respiratory tract cancers, chronic bronchitis and permanent damage to the airways when smoked
  • Cardiovascular system damage
  • Mental health problems including depression
  • Poor adolescent psychosocial development

Source: Adapted from [1,10,12]. 

Burden of disease and injury

Cannabis use contributed to 0.1% of the total burden of disease and injuries in 2011 and 7% of the total burden due to illicit drugs (Table S2.69). Accidental poisoning (41%) and cannabis dependence (36%) contributed most to the burden due to cannabis use. Only a small proportion (less than 2%) of the burden of schizophrenia, anxiety disorders, road traffic injuries and depressive disorders was attributable to cannabis use. This is largely due to the low prevalence of cannabis dependence [11].

Mental health

Ongoing and regular use of cannabis is associated with a number of negative long-term effects. Regular users of cannabis can become dependent and commonly reported symptoms of withdrawal include anxiety, sleep difficulties, appetite disturbance and depression [10,12].

The 2016 NDSHS found a significant increase in the proportion of past month and past 12-month cannabis users that reported mental illness and ‘high to very high’ levels of psychological distress.

Specifically, between 2013 and 2016:

  • Mental illness reported by cannabis users in the past month increased from 25% to 31% and for cannabis users in the past 12 months increased from 21% to 28% (Table S2.74)
  • ‘High to very high’ levels of psychological distress reported by past month cannabis users increased from 20% to 27% and for past 12-month cannabis users increased from 17% to 24% [6] (Figure CANNABIS3; Table S2.73).
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Poly drug use

Cannabis use is also highly correlated with the use of tobacco, alcohol and other drugs. This makes measuring the effects of cannabis alone difficult and potentially increases risks for users.

The 2016 NDSHS showed that alcohol was the most common substance used concurrently with cannabis. Of those recent cannabis users who also consumed alcohol, 65% exceeded the single occasion risk guidelines at least monthly and 41% exceeded the lifetime risk guidelines.

The most common other drugs concurrently used by recent cannabis users were:

  • tobacco (35%)
  • ecstasy (17%),
  • cocaine (16%)
  • the non-medical use of pharmaceuticals (14%) [6] (Table S2.68).

Deaths

Cause of deaths data from the ABS indicates that compared with other licit and illicit drugs, cannabis was less frequently present in drug-induced deaths. However, cannabis was the second most common drug identified at toxicology for transport accident deaths [13]. The short-term effects of cannabis can increase the risk of road traffic crashes, largely due to diminished driving performance in response to emergencies [10].

Treatment

The AIHW 2016–17 Alcohol and Other Drug Treatment Services National Minimum Dataset (AODTS NMDS) showed that:

  • Cannabis was a drug of concern (principal or additional) in 39% of closed treatment episodes, and was the third most common principal drug of concern (24% or 41,921 of closed treatment episodes) (Figure CANNABIS4).
  • In more than half (52%) of episodes with cannabis as the principal drug of concern, the client reported additional drugs of concern. This was most commonly alcohol (32%), nicotine (25%), or amphetamines (22%) (Tables S2.77 and S2.78).
  • Client demographics:
    • Where cannabis was the principal drug of concern, seven out of ten clients were males (68%), and around 1 in 6 were Indigenous (17%) (Table S2.79).
    • Where cannabis was the principal drug of concern, Indigenous Australians (911 per 100,000 population) were more likely to have received treatment than non-Indigenous Australians (123 per 100,000 population) [14].
  • Source of referral:
    • The most common source of referral for treatment episodes where cannabis was the principal drug of concern was diversion (that is, referred from the criminal justice system into AOD treatment for drug or drug-related offences) (36%), followed by self/family (28%) (Table S2.80).
  • Type of treatment:
    • Where cannabis was the principal drug of concern, counselling was the most common treatment type (41%), followed by information and education only (21%) (Table S2.81).
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At-risk groups

Aboriginal and Torres Strait Islander people

The 2016 NDSHS found that 1 in 6 (17%) Indigenous Australians aged 14 and over used cannabis in the last 12 months, which was 1.9 times higher than non-Indigenous Australians (11%) [6].

People engaged with the criminal justice system

In 2015–16 the highest recorded number of arrests (79,600) arrests relating to cannabis (72,200 consumer and 7,300 provider)—consumer arrests accounted for 91% of national cannabis arrests in Australia [2].

According to the Drug Use Monitoring in Australia (DUMA) program, the proportion of police detainees testing positive to cannabis increased, from 44.4% in 2015–16  to 46.7% in 2016–17. For the second consecutive reporting period, the proportion of detainees testing positive to methamphetamine (51.4%) was higher than proportion of detainees testing positive to cannabis. [2]. Among those detainees whose most serious offence was violent, 42% tested positive for cannabis [15].

According to the 2015 Prisoner Health Survey, 41% of prison entrants reported using cannabis in the previous 12 months, second only to methamphetamines (50%) [16].

People identifying as lesbian, gay, bisexual, transgender, intersex or queer (LGBTIQ)

The 2016 NDSHS found that people identifying as homosexual/bisexual were 3.2 times more likely to report recent use of cannabis compared with the general population in the previous 12 months [6]. 

People who inject drugs

The 2018 Illicit Drug Reporting System (IDRS) showed that cannabis is the most frequently used illicit drug across the whole sample of people who inject drugs, with 73% reporting use in the last six months [5]. This remained stable over the previous five years. People who inject drugs may use cannabis to alleviate withdrawal symptoms from other drugs, or in combination with other drugs to enhance their effects.

Policy context 

Public perceptions and policy support

There have been changes over time in public perceptions of cannabis use in Australia. Data from the 2016 NDSHS showed:

  • There was a significant decrease in the proportion of Australians reporting cannabis as the first drug they thought of when asked about a drug problem—15% in 2016 compared with 23% in 2013.
  • Only 2.6% thought that cannabis caused the most concern to the general community, a statistically significant decrease from 3.8% in 2013.
  • Personal approval of cannabis use by an adult increased significantly from 9.8% in 2013 to 14.5% in 2016 [6].

There have also been some associated changes in public perceptions about cannabis-related policies. For example, the majority of Australians aged 14 years and over do not support the possession of cannabis being a criminal offence (74% in 2016 compared with 66% in 2010). Other increases in the proportion of people aged 14 years or over that supported:

  • the use of marijuana to treat medical conditions (from 74% in 2010 to 87% in 2016)
  • a change in legislation permitting the use of marijuana for medical purposes (from 69% in 2013 to 85% in 2016)
  • the legalisation of cannabis (from 25% in 2010 to 35% in 2016) [6] (Table S2.42).

Medicinal cannabis

In February 2016, the Australian Parliament passed legislation to enable the cultivation of cannabis for medicinal and related research purposes. The changes came into effect on 30 October 2016. Medicinal cannabis products are available for specific patient groups under strict medical supervision. There are currently reviews complete or underway relating to the use of cannabis for epilepsy in children and adults, multiple sclerosis, nausea and vomiting resulting from chemotherapy and HIV/AIDs therapy, chronic pain management and palliative care [17]. Cannabis cultivated for other purposes remains illegal.

Resources and further information

Information about the medicinal use of cannabis in Australia can be found at the Office of Drug Control.

References

  1. NSW Ministry of Health 2017. A quick guide to drugs & alcohol, 3rd edn. Sydney: National Drug and Alcohol Research Centre.
  2. Australian Criminal Intelligence Commission (ACIC) 2018. Illicit drug data report 2016–17. Canberra: ACIC. Viewed 21 September 2018.
  3. Alcohol and Drug Foundation 2017. Synthetic cannabis. Viewed 30 November 2017.
  4. Peacock A, Gibbs D, Karlsson A, Uporova J, Sutherland R, Bruno R, Dietze P, Lenton S, Alati R, Degenhardt L, & Farrell, M 2018. Australian Drug Trends 2018. Key findings from the National Ecstasy and Related Drugs Reporting System (EDRS) Interviews. Sydney, National Drug and Alcohol Research Centre, UNSW Australia.
  5. Peacock A, Gibbs D, Sutherland R, Uporova J, Karlsson A, Bruno R, Dietze P, Lenton S, Alati R, Degenhardt L & Farrell M 2018. Australian Drug Trends 2018. Key findings from the National Illicit Drug Reporting System (IDRS) Interviews. Sydney, National Drug and Alcohol Research Centre, UNSW Australia.
  6. Australian Institute of Health and Welfare (AIHW) 2017. National drug strategy household survey 2016: detailed findings. Drug statistics series no. 31. Cat. no. PHE 214. Canberra: AIHW. Viewed 14 December 2017
  7. Australian Crime Commission (ACC) 2009. Illicit Drug Data Report 2008–09. Canberra: ACIC. Viewed 5 October 2018.
  8. United Nations Office on Drugs and Crime (UNODC) 2017. World Drug Report 2017. Vienna: UNODC. Viewed 14 December 2017.
  9. White V & Williams T 2016. Australian secondary school students’ use of tobacco, alcohol, and over-the-counter and illicit substances in 2014. Victoria: Centre for Behavioural Research.
  10. Hall W & Degenhardt L 2009. Adverse health effects of non-medical cannabis use. Lancet. 374: 1383-1391.
  11. AIHW 2018a. Impact of alcohol and illicit drug use on the burden of disease and injury in Australia: Australian Burden of Disease Study 2011. Australian Burden of Disease Study series no. 17. Cat. no. BOD 19. Canberra: AIHW.
  12. Nielsen S & Gisev N (in press). Drug pharmacology and pharmacotherapy treatments. In Ritter, King and Lee (eds). Drug use in Australian society. Oxford University Press.
  13. Australian Bureau of Statistics (ABS) 2017. Causes of death, Australia, 2016. Cat. no. 3303.0. Canberra: ABS. Viewed 4 January 2018.
  14. AIHW 2018b. Alcohol and other drug treatment services in Australia 2016-17. Drug treatment services no. 31. Cat. no. HSE 207. Canberra: AIHW.
  15. Patterson, E Sullivan, T, Ticehurst, A & Bricknell, S 2018. Drug use monitoring in Australia: 2015 and 2016 report on drug use among police detainees, Statistical Reports Number 4. Canberra: Australian Institute of Criminology. Viewed 20 April 2018.
  16. AIHW 2015. The health of Australia’s prisoners 2015. Cat. No. PHE 207. Canberra: AIHW. Viewed 2 February 2018. 
  17. Department of Health 2017. Medicinal cannabis. Canberra: Office of Drug Control. Viewed 4 January 2018
  18. Australian Criminal Intelligence Commission (ACIC) 2019. National wastewater drug monitoring program, report 6. Canberra: ACIC. Viewed 20 February 2019.