Cannabis use in Australia spiked during the first COVID-19 lockdown period whilst methamphetamine use fell dramatically, a study has found.

Research led by the University of South Australia (UniSA) analysed wastewater samples taken during 2020. Whilst the use of methamphetamine (ice) significantly reduced during the first lockdown, use of cannabis increased significantly.

The study has been published in Environmental Science and Technology Letters.

The researchers, in collaboration with The University of Queensland and University of Adelaide, looked at wastewater samples taken every two months from 20 treatment plants across Australia, covering approximately half of the population. Investigators tested the samples for methamphetamine, ecstasy, cocaine, cannabis, and alcohol. The team compared samples collected before the COVID-19 pandemic (August 2016 to December 2019) with those taken during Australia’s first national lockdown period from February to June 2020.

Cannabis use increased significantly

The findings show that cannabis use increased by large amounts across all Australian states during the lockdown, with the exception of the Northern Territory. The researchers said that, as cannabis is largely produced locally in Australia, supplies were plentiful. Methamphetamine use, however, fell by as much as 50% in Western Australia, which has been attributed to restricted imports of the drug due to border closures.

Alcohol use dropped

The samples from 2020 also showed that South Australians drank significantly less during lockdown, consuming 12% less alcohol than normal, with NSW and the Northern Territory also drinking less. The results also showed that alcohol consumption – albeit lower in total – was evenly spread over the whole week during the three-month lockdown, with the closure of bars, hotels, nightclubs, and social gatherings curtailing the normal weekend spike. Once restrictions were eased, alcohol use spiked.

UniSA Associate Professor Cobus Gerber, one of the study leads, said: “Job cuts and loss of income could have contributed to the lower usage nationally, but it is more likely to be connected to disrupted supply lines.

“This study provides an insight into the first four months of COVID restrictions in Australia and it remains to be seen what the longer-term effect of the pandemic will be.”