Cannabis use declined significantly in Australia between 2001 and 2013, according to a new report out of the University of New South Wales. But while the use-rate data seem solid, the underlying reasons for the decline are harder to pin down.

Between 2001 and 2013, consumption fell dramatically, especially among  young people. Among individuals aged 14 to 19, past-year use dropped from 24.4% to 14.8%. Among those in their 20s, past-year use declined from 29.1% to 20.8%. The only recorded uptick was a slight rise in consumption among those in their 40s.

(Image via “Trends in Drug Use and Related Harms in Australia, 2001 to 2013,” University of New South Wales. PDF)

A combination of five significant factors may be contributing to the phenomenon, according to a review paper published in Drug & Alcohol Review. The piece, by University of New South Wales academics Alison Ritter and Oluwadamisola Sotade, calls for more comprehensive research into the reasons for the decline in cannabis use in Australia.

“We have known for some time about the declines,” said Ritter, who also authored the report itself. “This was more about trying to start to think about why.”

Ritter and Sotade identified various changes in attitude, regulation, supply, and complementary drug use as factors that might help explain the decline, as well as an “increasing focus on healthy lifestyles.”

To better understand such factors, the authors argue, “A new research agenda is required, with a multidisciplinary focus including regulation theory, economics and econometric techniques, comparative policy analysis methods, and sociology and cultural analysis such that the plausible reasons can be empirically tested.”

Will Australia’s Medical Cannabis Law Impact Broader Use?

“It’s very hard to speculate on this,” Ritter told Leafly, “but research published from the USA after their experience with medicinal cannabis suggests that rates of cannabis use in young people [has] not increased in association with medicinal cannabis.”

There is conflicting evidence about cannabis use amongst adults,” she added. “Some studies do show a trend to increasing cannabis use, others do not. There does appear to be evidence of an increase in cannabis use disorders.”

Among medical marijuana states in the US, Ritter said less-regulated systems may be more  likely to contribute to a rise in nonmedical use. “The effects depend on the kinds of medicinal cannabis programs” in place, she said.

What About Decriminalization?

Ritter noted “there has always been very strong support for [decriminalization] in Australia,”  pointing  out that every state has some style of decriminalization law on the books. In a paper published last year, Ritter and other University of New South Wales academics published data on the effects of decriminalization.

The research evidence indicates that decriminalisation of drug use:

• Reduces the costs to society, especially the criminal justice system costs
• Reduces social costs to individuals, including improving employment prospects
• Does not increase drug use
• Does not increase other crime
• May, in some forms, increase the numbers of people who have contact with the criminal justice system (net widening)

Evidence that decriminalization doesn’t result in increased drug use is not, of course, the same as a finding that it results in decreased drug use. Nevertheless, it’s relevant data to consider as communities weigh how further decriminalization measures could affect cannabis use rates.