Here’s the press release
Cannabis reform: reaping more than you can sow
Survey of homegrowers shows ACT cannabis law reform is positive despite grey areas
6 February 2025
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’s 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 University of Sydney’s 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 Nature Scientific Reports.
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 University of Sydney, highlighted positive aspects of the legislative reform.
“The 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,” Professor McGregor said.
“Cultivators exit illegal networks, enjoy the process of cultivation, and grow cannabis of modest potency and decent quality that doesn’t 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.”
Study lead author Dr Cilla Zhou noted certain “wrinkles” within the legislation that need to be “ironed out”. 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.
“Australian cultivators grow a median of 85 grams of dry matter and 285 grams of fresh matter per plant,” Dr Zhou said.
“Current 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.”
Another legislative “wrinkle” 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.
“With other jurisdictions in Australia now actively considering cannabis law reform this evidence shows allowing adults to grow cannabis for personal use is effective,” said Chris Gough, Executive Director for the Canberra Alliance for Harm Minimisation and Advocacy.
“It provides an avenue for adults who use cannabis to avoid criminalisation and exposure to the dangers of unregulated markets that doesn’t lead to increases in the use or sale of cannabis.”
Declaration: The Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney 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.
Here’s the report
Zhou_et_al-2025-Scientific_Reports
