Cannabis use has increased worldwide as legalization expands and public perception shifts toward viewing it as relatively harmless. However, new research suggests its effects on the brain may be more concerning than many assume.

Interest in the topic has grown after Donald Trump supported moving cannabis from Schedule I to Schedule III, a change meant to ease restrictions on medical research. While the move could expand scientific study, it has also reignited debate about long-term health risks.

A study published in JAMA Network Open examined how cannabis affects brain activity. Researchers analyzed brain scans from about 1,000 young adults aged 22 to 36 diagnosed with cannabis use disorder.

The findings showed that both long-term users and recent users displayed reduced brain activity during working memory tasks. Working memory is critical for reasoning, focus, verbal comprehension, and mathematical skills.

According to lead author Joshua Gowin, the goal is not to alarm but to provide balanced information. As cannabis use grows, understanding both its potential benefits and risks helps people make informed decisions.

The study also found disrupted communication between key brain networks involved in decision-making, memory, focus, emotional regulation, and daydreaming. Of all cognitive tests analyzed, only working memory showed a statistically significant decline.

Researchers also challenged a common belief about CBD. While many users think CBD reduces THC’s negative effects, the study suggests it may sometimes intensify them instead.

Separate research has raised concerns about mental health risks. Dr. Daniel Myran warned of links between cannabis use and psychosis, particularly in young men. He noted sharp increases in emergency room visits tied to cannabis-induced psychosis and higher risks of later anxiety or psychotic disorders.