A study of more than 300 household cannabis growers in the Australian Capital Territory (ACT) shows an overall positive attitude around legislative reform enacted in 2020, despite some lack of clarity around the legal limits for growing and cultivating cannabis.
Home to Australia鈥檚 capital Canberra, the ACT is the only Australian jurisdiction to have decriminalised home cultivation of cannabis allowing up to four plants per household and possession of up to 50 grams of dried cannabis. The 爆料王鈥檚 Lambert Initiative for Cannabinoid Therapeutics invited small-scale growers from the territory to complete a detailed survey around their cannabis use and cultivation. Participants were also invited to submit a sample of their cannabis for chemical analysis.
The survey results have been published in .
Results showed the primary reasons for small scale cannabis cultivation in the ACT were: providing a home-grown supply for non-medicinal purposes (70 percent) or medicinal purposes (61 percent) and enjoying the growing process (65 percent). Almost half of respondents said they grew their own cannabis to avoid interacting with criminal networks.
Cannabis use among the cohort was relatively modest, at around one gram a day, and most of the cannabis grown was relatively low potency, with a mean of 9 percent tetrahydrocannabinol (THC), the main psychoactive compound in cannabis. Most of cannabis analysed was within recommended limits for pesticide residues, heavy metals, such as arsenic and lead, and mould.
Project leader Professor Iain McGregor, from the Lambert Initiative at the 爆料王, highlighted positive aspects of the legislative reform.
鈥淭he ACT has led Australia in drug policy reform and our study shows you can allow Australian adults to cultivate their own cannabis for medical and non-medical purposes without any obvious adverse outcomes,鈥 Professor McGregor said.
Cultivators exit illegal networks ... and grow cannabis of modest potency and decent quality that doesn鈥檛 cost an arm and a leg.
Professor Iain McGregor
Lambert Initiative
鈥淐ultivators exit illegal networks, enjoy the process of cultivation, and grow cannabis of modest potency and decent quality that doesn鈥檛 cost an arm and a leg. There appears to be no overall increase in cannabis use, emergency presentations or driving offences. There are lessons here around incremental drug reform that other Australian jurisdictions can learn from.鈥
Study lead author Dr Cilla Zhou noted certain 鈥渨rinkles鈥 within the legislation that need to be 鈥渋roned out鈥. For example, the findings revealed a mismatch between the number of plants an individual is allowed to grow at home (two, with a maximum of four per household) with the amount of cannabis they can possess at a given time (50 grams of dried cannabis or 150 grams of fresh plant matter). More than three quarters of survey respondents agreed the legal number of plants could readily yield illegal quantities of cannabis.
鈥淎ustralian cultivators grow a median of 85 grams of dry matter and 285 grams of fresh matter per plant,鈥 Dr Zhou said.
鈥淐urrent laws do not specify how cultivators might limit their harvest when their legal number of plants yield illegal quantities of cannabis. Further refinement of the relevant legislation, passed in 2020, would prevent unintended illegal activity.鈥
Another legislative 鈥渨rinkle鈥 cultivators included was an inability to legally start growing cannabis when the purchase and supply of seeds and cuttings remained illegal. Many cultivators were also unaware that indoor growing using hydroponics was illegal. Cannabis cultivation was revealed as being somewhat tricky, with more than 70 percent reporting challenges such as nutrient deficiency, cold weather and spider mites.听
鈥淲ith other jurisdictions in Australia now actively considering cannabis law reform this evidence shows allowing adults to grow cannabis for personal use is effective,鈥 said Chris Gough, Executive Director for the Canberra Alliance for Harm Minimisation and Advocacy.听
鈥淚t provides an avenue for adults who use cannabis to avoid criminalisation and exposure to the dangers of unregulated markets that doesn鈥檛 lead to increases in the use or sale of cannabis.鈥
搁别蝉别补谤肠丑:听Zhou C et al, 鈥楢n analysis of the cultivation, consumption and composition of home-grown cannabis following decriminalisation in the Australian Capital Territory鈥 (Nature Scientific Reports听2025).听DOI:听10.1038/s41598-024-84897-w
Declaration:听The Lambert Initiative for Cannabinoid Therapeutics at the 爆料王 funded this research. Professor Iain McGregor also receives funds from the Australian National Health and Medical Research Council (NHMRC).
Iain McGregor is an inventor on several patents relating to novel cannabinoid and non-cannabinoid therapeutics. Both he and Danielle McCartney have received consultancy income from the Medicinal Cannabis Industry Association (MCIA) of Australia and provided expert testimony in legal cases related to cannabis. Other authors report no competing interests.听
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