514 Substance-Related and Addictive Disorders
or internalizing disorders during childhood or  adolescence. Youths with high behavioral
disinhibition scores show early-onset substance use disorders, including cannabis use dis-
order, multiple substance involvem ent, and early conduct problems.
Environmental. Risk factors include academic failure , tobacco smoking, unstable or abu-
sive family situation, use of cannabis among immediate family members, a family history
of a substance use disorder, and low socioecono mic status. As with all substances of abuse,
the ease of availability of the substance is a ri sk factor; cannabis is relatively easy to obtain
in most cultures, which increases the risk  of developing a cannabis use disorder.
Genetic and physiological. Genetic influences contribute to the development of canna-
bis use disorders. Heritable factors contribute between 30% and 80% of the total variance
in risk of cannabis use disorders. It should be noted that common genetic and shared en-
vironmental influences between cannabis and other types of substance use disorders sug-
gest a common genetic basis for adolesce nt substance use and conduct problems. 
Culture-Related Diagnostic Issues
Cannabis is probably the world’s most commo nly used illicit substance. Occurrence of
cannabis use disorder across countries is unkn own, but the prevalence rates are likely sim-
ilar among developed countries. It is frequently among the fi rst drugs of experimentation
(often in the teens) of all cultur al groups in the United States. 
Acceptance of cannabis for medical purposes varies widely across and within cultures.
Cultural factors (acceptability and legal status ) that might impact diagnosis relate to dif-
ferential consequences across cultures for dete ction of use (i.e., arrest, school suspensions,
or employment suspension). The general change in substance use disorder diagnostic cri-