Early Use of Marijuana: "The younger and more often teens use marijuana, the more likely they are to engage in other substance use and the higher their risk of developing a substance use disorder. Among high school students, 7.5 percent used marijuana for the first time before the age of 13. CASA’s analysis of national data finds that the average age of initiation of marijuana use among high school students is 14.3 years old. Compared to those who began using marijuana after age 21, those who first used it before age 15 are:
"The teen brain is a work in progress, making it more vulnerable than the mature brain to the physical effects of drugs. The potential for developing substance abuse and dependence is substantially greater when an individual’s first exposure to alcohol, nicotine and illicit drugs occurs during adolescence than in adulthood."
Early Initiation of Substance Use: “When initiation of substance use occurs in preadolescence or early in adolescence, the risk of addiction is magnified.8 CASA’s analysis of national data finds that individuals‡ who first used any addictive substance before age 15 are six and a half times as likely to have a substance use disorder as those who did not use any addictive substance until age 21 or older (28.1 percent vs. 4.3 percent).”
12th Graders and Attitudes Toward Legalizing Marijuana: " Table 8-8 lists the proportions of 12th graders in 2015 who favor various legal consequences for marijuana use: making it entirely legal (42%), a minor violation like a parking ticket but not a crime (27%), or a crime (15%). The remaining 15% said they 'don’t know.' It is noteworthy just how variable attitudes about this contentious issue are.
" Asked whether they thought it should be legal to sell marijuana if it were legal to use it, about three in five (64%) said “yes.” However, about 86% of those answering 'yes' (55% of all respondents) would permit sale only to adults. A small minority (9%) favored the sale to anyone, regardless of age, while 23% said that sale should not be legal even if use were made legal, and 13% said they 'don’t know.' Thus, while the majority subscribe to the idea of legal sale, if use is allowed, the great majority agree with the notion that sale to underage people should not be legal.
(Alcohol Use v Marijuana Use - US Youth and "The Displacement Hypothesis") "Alcohol and marijuana are the two most commonly used substances by teenagers to get high, and a question that is often asked is to what extent does change in one lead to a change in the other. If the substances co-vary negatively (an increase in one is accompanied by a decrease in the other) they are said to be substitutes; if they co-vary positively, they are said to be complements.
Taxonomy of Cannabis: "The biological (reproductive) definition of a species states that all specimens of a population are of a single species if they are naturally able to sexually reproduce, generating fertile offspring. This is the case throughout the genus Cannabis, and by this definition, therefore, there are no clear biological grounds to separate it into different species.However, within the species Cannabis sativa L., several subspecies are sometimes identified (Small and Cronquist, 1976).
History of Marijuana Use: "There are indications that cannabis was used as early as 4000 B.C. in Central Asia and north-western China, with written evidence going back to 2700 B.C. in the pharmacopeia of emperor Chen-Nong.
Cannabis Use and Driving Impairment: "There is considerable evidence from laboratory studies that cannabis (marijuana) impairs reaction time, attention, tracking, hand-eye coordination, and concentration, although not all of these impairments were equally detected by all studies (Couper & Logan, 2004a; Heishman, Stitzer, & Yingling, 1989; Gieringer, 1988; Moskowitz, 1985). In reviewing the literature on marijuana, Smiley (1998) concluded that marijuana impairs performance in divided attention tasks (i.e., a poorer performance on subsidiary tasks). Jones et al.
Cannabis Use, Alcohol Use, Smartphone Use, and Accident Risk: "Although for the mobile phone conversation and cannabis studies the reaction times were slightly different, they were still comparable. The same visual stimulus was used and was presented in the same visual scene.
Pulmonary Effects of Cannabis: "For physiological and pharmacological reasons,61 smoking cannabinoid herbals does not seem to have a similar health hazard profile as tobacco smoking, aside from the potential for bronchial irritation and bronchitis. Smoking cannabis was not associated with an increased risk of developing chronic obstructive pulmonary disease ..."