For years, marijuana has been seen as relatively harmless — even beneficial in some medical contexts. But new research is raising serious concerns for long-term users, especially those who continue smoking regularly into their 30s and beyond.

According to several studies, long-term cannabis use may be linked to slower cognitive performance, memory decline, and reduced motivation levels. Scientists from the Dunedin Multidisciplinary Health and Development Research Unit found that adults who used marijuana heavily for over a decade experienced noticeable drops in IQ and difficulty with attention and focus — effects that didn’t completely reverse even after quitting.

What’s more, regular users in their 30s often show higher risks of respiratory issues, including chronic cough and inflammation in the airways, due to the constant smoke exposure. Some evidence also points to increased risks of anxiety, depression, and sleep disruption, particularly when consumption is daily or used as an emotional coping tool.

Doctors emphasize that the main problem isn’t occasional or moderate use — it’s long-term dependence. Many users underestimate how marijuana affects brain development well into the mid-20s, and continuing after that can slow the brain’s recovery processes.

In short: if you’re still smoking regularly at 30, your body may already be feeling the effects — even if you don’t notice them yet. Experts advise taking tolerance breaks or switching to non-smoking forms to protect your lungs, mental health, and long-term focus.