Adults who use cannabis are nearly four times more likely to develop type 2 diabetes than non-users, a major study has found.
The research analysed about 96,800 people with cannabis-related diagnoses – from casual use to dependency – and compared them with more than 4.16m individuals who had no record of drug use or chronic illness over five years.
Researchers at Boston Medical Center in Massachusetts examined medical records from 54 healthcare organisations in the US and Europe using the TriNetX Research Network.
They found that 2.2 per cent of cannabis users developed type 2 diabetes during the five-year period, compared with 0.6 per cent of non-users.
Even after adjusting for other health risks such as high blood pressure, cholesterol, heart disease and alcohol or cocaine use, cannabis users still faced a significantly higher risk.
Dr Ibrahim Kamel from Boston Medical Center said: “As cannabis becomes more widely available and socially accepted and legalised in various jurisdictions, it is essential to understand its potential health risks.”
Experts suggest cannabis may affect appetite, metabolism and insulin resistance – the body’s ability to respond properly to insulin.
Cannabis use is often associated with poor eating habits, which could contribute to rising blood sugar levels over time.
The findings raise concerns as cannabis becomes more widely legalised and socially accepted.
While often viewed as an alternative to alcohol or tobacco, the research suggests its long-term health risks could be more serious than many realise.
The researchers acknowledged several limitations.
Because the study was retrospective – looking back at patient records rather than tracking new cases over time – it cannot prove cannabis directly causes diabetes.
They also could not distinguish between occasional and daily users, as the data relied on self-reporting – even in countries where cannabis was illegal – and did not measure exact consumption levels.
The findings could have implications for clinical practice.
Kamel said: “Physicians may need to “routinely talk to patients about cannabis use so they can understand their overall diabetes risk and potential need for metabolic monitoring.
“These new insights from reliable, real-world evidence highlight the importance of integrating diabetes risk awareness into substance-use disorder treatment and counselling”