Marijuana and Driving - More Data Needed: "The decreased speed during the simulated drive could be interpreted as an attempt to compensate for perceived cognitive impairment, Alternatively, marijuana may not have affected decision making and judgment and the reduction in speed would improve safety margins, While the clinical significance of a 3% to 5% decrease in speed may be questioned, previous research suggests such a decrease will result in approximately a 7% decrease in all injuries and a 15% decrease in fatalities (Nilsson 1981), Use of an alternate task design in which subjects are r

Cannabis and Driving Impairment: "The present study's subtle finding of decreased speed under the influence of acute marijuana is generally consistent with the literature, which has found that marijuana's effects on driving can be subtle.

Cannabis and Psychotic Experiences: "This 10 year follow-up study showed that incident cannabis use significantly increased the risk of incident psychotic experiences. The association was independent of age, sex, socioeconomic status, use of other drugs, urban/rural environment, and childhood trauma; additional adjustment for other psychiatric diagnoses similarly did not change the results. There was no evidence for self medication effects as psychotic experiences did not predict later cannabis use.

Cannabis Use and Motor Vehicle Accident Risk: "Our primary analysis looked at the risk of a motor vehicle collision while under the influence of cannabis and included all nine studies (relating to 49 411 participants). The pooled risk of a motor vehicle collision while driving under the influence of cannabis was almost twice the risk while driving unimpaired (odds ratio 1.92 (95% confidence interval 1.35 to 2.73); P=0.0003); we noted heterogeneity among the individual study effects (I2=81%).

According to the Substance Abuse and Mental Health Service's Treatment Episode Data Set, in 2015 in the US there were 213,001 admissions to treatment with marijuana reported as the primary substance of abuse out of the total 1,537,025 admissions to treatment in the US for those aged 12 and older for all substances that year. This is the lowest number of marijuana admissions and total treatment admissions in at least a decade: marijuana admissions peaked in 2009 at 373,338, and total admissions peaked in 2008 at 2,074,974.

IQ Decline Among Adolescent-Onset Marijuana Users: "In the present study, the most persistent adolescent-onset cannabis users evidenced an average 8-point IQ decline from childhood to adulthood. Quitting, however, may have beneficial effects, preventing additional impairment for adolescent-onset users.

(Cognitive Deficit Among Adolescent-Onset Marijuana Users) "Our findings suggest that regular cannabis use before age 18 y predicts impairment, but others have found effects only for younger ages ^{(10, 15)}. Given that the brain undergoes dynamic changes from the onset of puberty through early adulthood ^{(37, 38)}, this developmental period should be the focus of future research on the age(s) at which harm occurs."

Marijuana Use vs. Tobacco Use: "High school students are more likely to use marijuana than to smoke cigarettes. High school students are:
"• More likely to have tried marijuana than tobacco (24 percent vs. 15 percent); and
"• More likely to say their close friends use marijuana than smoke cigarettes (51 percent vs. 39 percent)."

Marijuana Use by Peers and Perception of Harm: "Teens also say they are seeing more peers in school smoking marijuana and more teens (73 percent) report having friends who smoke marijuana regularly (71 percent) – significantly higher than four years ago. Since 2008, there have also been significant declines in teen perceptions that they will lose respect, harm themselves, or mess up their lives if they use marijuana."

"Annual marijuana prevalence peaked among 12th graders in 1979 at 51%, following a rise that began during the 1960s. Then use declined fairly steadily for 13 years, bottoming at 22% in 1992—a decline of more than half. The 1990s, however, saw a resurgence of use. After a considerable increase (one that actually began among 8th graders a year earlier than among 10th and 12th graders), annual prevalence rates peaked in 1996 at 8th grade and in 1997 at 10th and 12th grades. After these peak years, use declined among all three grades through 2007 or 2008.