Researchers in Ontario, Canada have found a troubling connection between severe cannabis use among adults 45 and older and increased dementia diagnoses. The researchers found that middle-age and older adults who were hospitalized or went to the ER because of their heavy cannabis use had a much higher risk of being diagnosed with dementia within the next 5 years than those of the same age and sex. Specifically, this group had a 3.9 times greater risk of developing dementia than the general population, and a 1.5 times higher risk than those who were hospitalized for other reasons. "This doesn't mean cannabis causes dementia," noted lead study author Daniel T. Myran, MD, MPH, in the study. "But it suggests that problematic use—severe enough to require hospital care—may be a warning sign or contributing factor."