Cannabis use among Ontario adults has almost doubled since 1977, from 8 percent to 14 percent in 2005, Science Daily reported April 14. 

The study found the average age of marijuana users also went up -- from 26 years of age in 1977 to 31 in 2005. Use, however, was found to be relatively infrequent -- on average, less than once-a-month.

On the positive side, tobacco smoking rates are at historic lows and rates of drinking and driving are the lowest on record.

"While we are making progress, we should not forget that the prior levels of substance use in Canada were high, and we're still a long way from what is usually considered a healthy lifestyle," said Dr. Jürgen Rehm, senior scientist at from the Centre for Addiction and Mental Health.

"Also, substance use, mainly tobacco and alcohol use, still costs Canada almost $9 billion in health care costs alone each year."

The study was conducted by the Centre for Addiction and Mental Health.