Three-Year Follow-Up: Cannabis Use Declined in Aboriginal Communities But Users Had More Hallucinations and Suicidal Thoughts | Research

The takeaway

A 3-year follow-up in remote Aboriginal communities found cannabis use decreased overall, but persistent users had significantly higher rates of auditory hallucinations, suicidal ideation, and imprisonment compared to never-users.

Read this if you want to understand how cannabis use affects remote communities and whether community-level interventions can reduce use.

Persistent cannabis users had significantly higher rates of hallucinations, suicidal ideation, and imprisonment

What the researchers found

Researchers conducted a 3-year follow-up in remote Aboriginal communities in Arnhem Land, Northern Territory, Australia. A randomly selected sample of 161 people (aged 13-36) was assessed in 2001 and reassessed in 2004, with an additional opportunistic sample of 104.

Those who used cannabis at both time points were at significantly greater risk than never-users of experiencing auditory hallucinations, suicidal ideation, and imprisonment.

In the randomly selected cohort, cannabis use decreased significantly from baseline to follow-up (P = 0.003). The reduction was evident in females generally (P = 0.008) and older males aged 16+ at baseline (P = 0.007). Among continuing users, fewer reported withdrawal-type symptoms including fragmented thoughts, memory problems, difficulty controlling use, and hallucinations. The reductions may reflect enhanced supply control and broader socio-political changes in the communities.

Why it matters

This is one of very few longitudinal studies of cannabis use in an indigenous population. The finding that persistent use was associated with hallucinations, suicidal thoughts, and imprisonment underscores the real-world consequences of heavy cannabis use in a vulnerable population, while the overall decline in use suggests that community-level interventions can be effective.

The numbers in context

161 randomly selected participants (13-36 years). 3-year follow-up. Cannabis use declined (P = 0.003). Decline in females (P = 0.008) and older males (P = 0.007). Persistent users: higher rates of auditory hallucinations, suicidal ideation, and imprisonment vs. never-users.

How the study worked

Longitudinal cohort study with 3-year follow-up. Randomly selected sample (n=161) and opportunistic sample (n=104) from Aboriginal communities in Arnhem Land, NT, Australia. Cannabis and substance use assessed by combining proxy assessments from Aboriginal health workers, medical records, and interview data. Changes analyzed using McNemar's test and Wilcoxon signed rank test.

What this study cannot tell us

Relatively small sample from a specific remote population, limiting generalizability. Cannabis use was assessed through combined proxy, medical, and self-report methods rather than biological testing. The observational design cannot determine whether cannabis caused the psychiatric symptoms or shared risk factors explain both. The decline in use may reflect specific local factors not applicable elsewhere.

How to read the evidence

Longitudinal cohort study with 3-year follow-up in a unique population. Stronger than cross-sectional studies but limited by small sample and specific population.

When this study was published

Published in 2006. Cannabis remains a significant health concern in some remote Australian communities, with ongoing research and intervention programs.

The bigger picture

Cannabis has been identified as a major health concern in some remote Australian Aboriginal communities. This study documented both the harms associated with continued use and the potential for community-level changes to reduce cannabis use. The reduction over three years, attributed partly to supply control, suggests that policy interventions can affect use patterns even in remote communities.

Questions still open

Did the psychiatric symptoms in persistent users improve when cannabis use decreased? Can the supply control and socio-political changes that reduced use in these communities be replicated elsewhere?

Common questions

Did cannabis use decrease in these communities?

Yes. In the randomly selected sample, cannabis use decreased significantly over three years (P = 0.003), particularly among females and older males. The researchers attributed this partly to enhanced supply control and broader community changes.

What health effects were seen in people who kept using cannabis?

Those who used cannabis at both the start and end of the three-year period were significantly more likely than never-users to have experienced auditory hallucinations, suicidal ideation, and imprisonment.

Read the original research

Changes in cannabis use and its consequences over 3 years in a remote indigenous population in northern Australia.

Addiction (Abingdon, England), 101(5), 696-705

View on PubMed ↗

Citation

Clough, Alan R; Lee, Kim S Kylie; Cairney, Sheree; Maruff, Paul; O'Reilly, Bridie; d'Abbs, Peter; Conigrave, Katherine M. (2006). Changes in cannabis use and its consequences over 3 years in a remote indigenous population in northern Australia.. Addiction (Abingdon, England), 101(5), 696-705.