A long-running survey by the Centre for Addiction and Mental Health shows there was a significant uptick in the use of cannabis even before legalization of recreational pot in October.
The ``Monitor'' survey found the proportion of Ontario adults reporting previous-year marijuana use rose from almost 16 per cent in 2016 to more than 19 per cent in 2017, a figure representing more than two million people.
CAM-H senior scientist Robert Mann says that over the long term, the biggest increase was seen in those aged 18 to 29. In 1996, about 18 per cent of people in that age group reported using cannabis in the previous year; that figure soared to 39 per cent in 2017.
The survey of more than 2,800 adults also found that the number of respondents who admitted driving after using marijuana doubled to 2.6 per cent in 2017 from 1.3 per cent five years earlier.
CAM-H also found an increased proportion of respondents reporting fair or poor mental health, a greater need to take mental distress days, and thoughts of suicide.
Younger adults who are part of the millennial generation were more likely to report such psychological distress and also problematic use of alcohol, cannabis and recreational opioids.