usage

In Ontario, for instance, a survey released Wednesday by the Centre for Addiction and Mental Health (CAMH) found that past-year cannabis use virtually doubled between 1996 and 2015, rising from about eight per cent to almost 15 per cent of respondents.
Significant increases were found among all age groups, but especially among 18- to 29-year-olds, with the proportion of pot smokers jumping from about 18 per cent in 1996 to 38 per cent in 2015

Although studies are beginning to show that some ingredients in marijuana are likely to be helpful for people with certain conditions, the findings have yet to nail down the specifics about the dose, the frequency, the best form to take (such as getting the active compounds from edible products or smoking it), the risks from frequent use, and whether marijuana works as well as or better than other available treatments, Budney said.
Usage Doubles & Addiction Doubles:  Over this 12-year period, the estimated number of U.S. adults who had used marijuana in the previous 12 months grew from 4.1 percent in 2001 to 9.5 percent in 2013. Marijuana-use disorders, which include problems with drug addiction and dependence, also rose, increasing from 1.5 percent of the adult population in 2001 to 2.9 percent in 2013, the study showed.
 
 College students smoke more pot than cigarettes: The survey found that 5.9 percent of college students said they had smoked pot 20 or more times in the past month. For comparison, 5.2 percent of students reported they had smoked cigarettes 20 or more times in the past month, according to the study. 
Inaccurate Labeling Edibles: Only 13 of the 75 tested pot food products — such as baked goods, beverages and candy — bought from dispensaries in California and Washington state had labels that accurately listed the amount of tetrahydrocannabinol, or THC, 
Teen Brain:  The researchers found that teens who had smoked marijuana — even once — had smaller brain volume in the amygdala compared with teens who never tried pot.
 

The impact of those changes can be seen not just in marijuana sales, but also in lives lost and harmed. In 2014, the report notes, there was a 32 percent increase in marijuana-related traffic deaths in Colorado compared with 2013. Marijuana-related traffic deaths increased 92 percent from 2010 to 2014.
In contrast, the increase in all traffic deaths during that time period was just 8 percent. Had it not been for marijuana-related traffic deaths, the state would have experienced adecline in traffic fatalities.
There's reason to think this problem won't go away soon. According to the report, an estimated 485,000 Colorado adults regularly use marijuana. Adults who consume marijuana almost daily make up the top 21.8 percent of that population — but they account for 66.9 percent of the demand for marijuana.

This week, the Department of Health and Human Services found that marijuana use among all Americans 12 and over – especially those over 26 – significantly increased in 2014 compared to 2013. The number of 16 and 17 year-olds using marijuana in the past month also increased, (14.2% versus 15.0%).

Seeing advertisements for medical marijuana was related to middle school adolescents' intentions to use marijuana and their actual marijuana use one year later. Researchers say this is particularly important given that the mean age of adolescents surveyed was 13 and initiation of marijuana use during early adolescence is associated with poor school performance, neuropsychological performance deficits and further use of other illicit drugs, such as heroin and cocaine.

Shows that Colorado 12 to 17 age group, 18 to 25, 26+ are significantly higher than US average for past 30 day marijuana use and all showed increased rates between 2011-12 and 2012-13

A new study suggests people with mental illness are more than seven times as likely to use marijuana weekly than people without a mental illness.

In total, 4.4 percent of individuals with a mental illness in the past 12 months reported using cannabis weekly, compared to 0.6 percent among individuals without any mental illness.

Cannabis use disorders occurred among 4 percent of those with mental illness versus 0.4 per cent among those without.

Researchers also noted that, although cannabis use is generally higher among younger people, the association between mental illness and cannabis use was pervasive across most age groups.