Scientists are raising serious concerns about cannabis use risks. A wave of new studies reveals troubling effects on the human body and mind. The findings are hard to ignore, and they span mental health, teenage brain development, emergency room surges, and vaping complications.

A Booming Industry, A Mounting Concern

Cannabis is no longer a fringe habit. Legal revenues in 2026 are projected to hit $30.5 billion, a rise of more than four per cent from the previous year, according to Whitney Economics. In the United States, eight out of ten Americans now live in a county with at least one cannabis dispensary, per Pew Research data from July 2025.

In Canada, recreational cannabis has been legal since 2018. Usage has climbed a staggering 40 per cent since 2017, according to the Canadian Centre for Substance Use and Addiction. Wider availability and growing social acceptance have driven the surge. But research now questions whether that acceptance has outpaced our understanding of the real harms of cannabis use.

Cannabis Use Risks and Mental Health: No Evidence of Benefit

A major study published in April 2026 in The Lancet examined cannabis across a range of mental health conditions. Researchers found very little evidence to support its use as a treatment.

Jack Wilson, lead author and postdoctoral research fellow at the University of Sydney’s Matilda Centre for Research in Mental Health and Substance Use, stated it plainly: “We found no evidence any form of cannabis is effective in treating anxiety, depression or post-traumatic stress disorder, which are three of the leading reasons for which cannabis is prescribed.”

Separate research in JAMA in March 2026 echoed this conclusion, as did earlier findings from 2019. Science has now repeatedly failed to confirm the therapeutic benefits many users expect. That matters most for the many people who turn to cannabis specifically to manage anxiety or low mood.

Cannabis Use Risks for Teens: Brain, Behaviour and the Road

Young people face some of the most serious harms of cannabis use. A McGill University study cross-referenced cannabis use with health records. It found that daily or near-daily use before the age of 15 was linked to individuals later seeking treatment for depression, anxiety, and suicidal distress, as well as respiratory conditions and injuries.

Road safety tells a similarly urgent story. Researchers at the University of Saskatchewan measured speed, reaction time, and crash rates in teens and young adults. They found that 75 per cent crashed in driving simulation tests up to six hours after consuming just 1 mg of cannabis with THC. Full findings are still pending publication.

A cross-sectional study of 1,003 young adults also connected cannabis use to short and long-term changes in brain function, especially during working memory tasks. The harms of cannabis use on the developing brain deserve far more attention than they currently receive.

Cannabis Hyperemesis Syndrome Cases Soar

A serious but frequently overlooked condition is turning up more often in hospital waiting rooms. Cannabis hyperemesis syndrome (CHS) triggers severe nausea, vomiting, and abdominal pain in frequent users. Its prevalence has surged dramatically.

Emergency room data tells the story clearly. CHS-related visit rates climbed from 4.4 per 100,000 in 2016 to 22.3 per 100,000 in 2022, a more than fivefold increase in just six years. A further study found that vape cartridge users developed CHS symptoms faster than those using other methods. This raises fresh questions about the cannabis use risks that vaping specifically poses to lung health.

The Broader Picture

Researchers have also flagged elevated cannabis use risks for older adults. They have highlighted the compounding dangers of combining cannabis with alcohol. Cannabis use disorder, a well-established condition where people struggle to stop using despite clear negative consequences, continues to affect a significant share of regular users.

Not everyone who uses cannabis will experience serious harm. But the weight of recent evidence makes it harder to dismiss the harms of cannabis use as minor or manageable across the board.

What You Can Do

If these findings concern you, some practical steps are worth taking.

Be honest about how often and how much you consume. Has your use increased recently? Think about whether cannabis is genuinely delivering the benefits you expect. Notice any changes in your mood, memory, or physical health. Cut back gradually if you want to reduce your intake. And if you struggle to do that on your own, speak to your GP. They can refer you to a specialist equipped with the right tools and strategies.

Understanding the full picture of cannabis use risks puts you in a stronger position to make choices that genuinely support your wellbeing.

Source: psychologytoday