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 transport accident deaths in 2016.

  • Recent use of cannabis among the Australian general population remained relatively 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—36% of recent users reported weekly use compared with ecstasy (2%) and cocaine (3%).
  • 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 in medical settings, rising from 69% in 2013.

More information is available in the Cannabis factsheet.

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 as 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) (ACIC 2019a; NSW Ministry of Health 2017).

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 (ACIC 2019a).

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 (ACIC 2018). Cannabis is a central nervous system depressant, but also alters sensory perceptions and may produce hallucinogenic effects when large quantities are used (ACIC 2018; NSW Ministry of Health 2017). 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 (Alcohol & Drug Foundation 2017). 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 (Peacock et al. 2019a; Peacock et al. 2019b). Perceived availability was the highest for hydroponic cannabis (88% of IDRS users and 90% of EDRS users rated it ‘easy’ or very easy’ to obtain), followed by bush cannabis (78% of IDRS users and 78% of EDRS users rated it ‘easy or very easy’ to obtain) (Peacock et al. 2019a; Peacock et al. 2019b). The primary source of cannabis reported by recent users aged 14 years or older was friends (66%), followed by dealers (19.9%) in 2016 (AIHW 2017) (Table S2.5).

In 2017–18, the majority of the number of national illicit drug seizures (52.4%) and arrests (48.8%) were for cannabis (ACIC 2019a). However, cannabis only accounted for 28.3% of the weight of illicit drugs seized nationally. There were 72,381 national cannabis arrests in 2017–18, with the number of national cannabis arrests increasing 30% over the last decade (from 55,638 in 2008–09) (ACIC 2019a; ACC 2010). The number and weight of national cannabis seizures has also increased over the decade—the number of seizures increased from 46,875 in 2008–09 to 59,139 in 2017–18 and the weight of seizures increased from 5,573 kilograms in 2008–09 to 8,655 kilograms in 2017–18 (ACIC 2019a; ACC 2010).

Widespread domestic cultivation generally makes the trafficking of herbal cannabis into Australia unnecessary and unprofitable (ACIC 2018).

Consumption

Cannabis continues to be the world’s most widely used illicit drug, with an estimated annual prevalence of 3.8% of the adult population aged 15–64 years, or the equivalent of 188 million people (ranging between 164 to 219 million) having used cannabis at least once in 2017 (UNODC 2019).

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 (AIHW 2017) (Tables S2.38 and S2.39).

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 aged 14 and over were more likely to be male (13.1%) than female (7.9%) (AIHW 2017) (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%) (AIHW 2017).

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

  • In 2017, cannabis was the most commonly used illicit substance by this cohort, with 17% of students reporting ever using cannabis and 8% using it in the month before the survey.
  •  For secondary students aged 12-17 use of cannabis in the past week in 2017 was slightly higher than in 2011.

Significant differences were found in the proportion of student’s aged 16–17 using cannabis in the past month and lifetime between 2017 (31% and 16% respectively) and 2011 (27% and 13% respectively) (Guerin & White 2018) (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).

Where the most common drug of concern was cannabis, the proportion of people living in Regional and remote areas who travelled 1 hour or longer to treatment services was higher than in Major cities (25% compared with 7%) (AIHW 2019a). 

The National Wastewater Drug Monitoring Program (NWDMP), measures the presence of substances in sewerage treatment plants across Australia. The measurement of cannabis consumption was included for the first time in the August 2018 collection. The most recent data indicates that the average consumption of cannabis in regional areas exceeded capital city consumption (ACIC 2019b). In addition, there was a decrease in average cannabis consumption for regional and capital city sites when comparing December 2018 and April 2019 data (ACIC 2019b).

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 (NSW Ministry of Health 2017). 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 naïve 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 conditions including depression
  • Poor adolescent psychosocial development

Source: Adapted from (Hall & Degenhardt 2009; Nielsen & Gisev 2017; NSW Ministry of Health 2017).

Burden of disease and injury

Cannabis use contributed to 0.2% of the total burden of disease and injuries in 2015 and 8.3% of the total burden due to illicit drugs (AIHW 2019c; Table S2.69). Drug use disorders (excluding alcohol) (13%) contributed most to the burden due to cannabis use. Only a small proportion (3% or less) of the burden of schizophrenia, poisoning, anxiety disorders, road traffic injuries and depressive disorders was attributable to cannabis use (AIHW 2019c).

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 (Hall & Degenhardt 2009; Nielsen & Gisev 2017).

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 S2.73)
  • ‘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% (AIHW 2017) (Figure CANNABIS3; Table S2.73).

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%) (AIHW 2017) (Table S2.68).

Deaths

In 2018, there were 264 drug-induced deaths where cannabinoids were present (Man et al. 2019). Compared with other licit and illicit drugs, cannabinoids are less frequently present in drug-induced deaths (Man et al. 2019; AIHW 2019a). However, cannabis was the second most common drug identified at toxicology for transport accident deaths (ABS 2017). The short-term effects of cannabis can increase the risk of road traffic crashes, largely due to diminished driving performance in response to emergencies (Hall & Degenhardt 2009).

Hospitalisations

The National Hospital Morbidity Database showed that in 2017–18, the rate of drug-related hospital separations for cannabinoids was similar for people usually residing in Major cities (24.3 per 100,000 population) and Regional and Remote areas (26.9 per 100,000 population). However, the rate was twice as high for people usually residing in Remote and Very remote areas, compared with those in Major cities (54.1 per 100,000 population compared with 24.3 per 100,000 population) (Table S1.8c).

Treatment

The AIHW 2017–18 Alcohol and Other Drug Treatment Services National Minimum Data Set (AODTS NMDS) showed that:

  • Cannabis was a principal drug of concern in 22% of closed treatment episodes, and was the third most common principal drug overall (Table S2.76 and Figure CANNABIS4).
  • In almost half (46%) of episodes with cannabis as the principal drug of concern, the client reported additional drugs of concern. This was most commonly alcohol (33%), nicotine (25%), or amphetamines (21%) (Tables S2.77 and S2.78).
  • Client demographics:
    • In treatment episodes where cannabis was the principal drug of concern, almost seven out of ten clients were males (67%, or 29,163 clients), and around 1 in 6 were Indigenous (17.7% or 7,644 clients) (Table S2.79).
    • Where cannabis was the principal drug of concern, Indigenous Australians (970 per 100,000 population) were more likely to have received treatment than non-Indigenous Australians (122 per 100,000 population) (AIHW 2019b).
  • 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) (32%), 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 (39%), followed by information and education only (20%) (Table S2.81).

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 1.5 times higher than non-Indigenous Australians (11%) (AIHW 2017). The 2018-19 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS) showed that 24% of Indigenous Australians aged 15 and over had used marijuana, hashish or cannabis resin in the last 12 months (ABS 2019).

People engaged with the criminal justice system

In 2017–18 the highest recorded number of arrests (72,381) were arrests relating to cannabis – consumer arrests accounted for 92% of national cannabis arrests in Australia (ACIC 2019a).

According to the Drug Use Monitoring in Australia (DUMA) program, the proportion of police detainees testing positive to cannabis was relatively stable between 2017 and 2018 (46% and 47% respectively) (Patterson et al. 2019; Voce & Sullivan 2019). In 2018, the proportion of detainees testing positive to cannabis (47%) was lower than the proportion of those testing positive to methamphetamine (52%) (Voce & Sullivan 2019). Among those detainees whose most serious offence was violent, 51% tested positive for cannabis in 2018 (Voce & Sullivan 2019).

According to the 2018 Prisoner Health Survey, 40% of prison entrants reported using cannabis in the previous 12 months, second only to methamphetamines (43%) (AIHW 2019d).

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 (AIHW 2017).  

People who inject drugs

The 2019 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 74% reporting use in the last six months (Peacock et al. 2019b). In all jurisdictions (except NSW), the percent of participants reporting recent cannabis use (previous 6 months) has declined during the monitoring period (Peacock et al. 2019b). 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 (AIHW 2017).

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). There were 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) (AIHW 2017) (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 (DoH 2017). 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

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