ministration, or family, which also places the youth at risk for physical or behavioral
consequences. In more severe cases, there is a progression to using alone or using through-
out the day such that use interferes with da ily functioning and takes the place of previ-
ously established, prosocial activities.
With adolescent users, changes in mood stab ility, energy level, and eating patterns are
commonly observed. These signs and symptoms ar e likely due to the direct effects of can-
nabis use (intoxication) and the subsequent effects following acute intoxication (coming
down), as well as attempts to conceal use from others. Sc hool-related problems are com-
monly associated with cannabis use disorder in  adolescents, particularly a dramatic drop
in grades, truancy, and reduced interest in general school activities and outcomes.
Cannabis use disorder among adults typically involves well-establish ed patterns of daily
cannabis use that continue despite clear psycho social or medical problems. Many adults have
experienced repeated desire to st op or have failed at repeated cessation attempts. Milder adult
cases may resemble the more common adolescent cases in that cannabis use is not as frequent
or heavy but continues despite po tential significant consequences of sustained use. The rate of
use among middle-age and older adults appears to be increasing, likely because of a cohort ef-
fect resulting from high prevalence of use in the late 1960s and the 1970s.
Early onset of cannabis use (e.g., prior to ag e 15 years) is a robust predictor of the de-
velopment of cannabis use disorder and other types of substance use disorders and mental
disorders during young adulthood. Such early onset is likely related to concurrent other
externalizing problems, most notably conduc t disorder symptoms. However, early onset