Cannabis dependence in the San Francisco Family Study: age of onset of use, DSM-IV symptoms, withdrawal, and heritability

Abstract

Cannabis is the most widely used illicit drug in the United States, yet the role of genetics in individual symptoms associated with cannabis use disorders has not been evaluated. The purpose of the present set of analyses was to describe the symptomatology and estimate the heritability of DSM-IV criteria/symptoms of cannabis dependence in a large sample of families. Participants were 2524 adults, participating in the University of California San Francisco (UCSF) Family Study of alcoholism. Seventy percent of the sample had ever used cannabis and 13.9% met DSM-IV criteria for cannabis dependence. Younger age at first cannabis use was found to be significantly associated with a shortened survival to becoming cannabis dependent. Although a greater percentage of men met criteria for cannabis dependence, women were found to demonstrate "telescoping" as indexed by a shorter survival time from initial use to dependence as compared to men. A cannabis withdrawal syndrome was identified in users, the primary symptoms of which were nervousness, appetite change, and sleep disturbance. Cannabis use (h(2)=0.31) and dependence (h(2)=0.20), age at first use, individual DSM-IV criteria for dependence, and cannabis-use associated symptoms of depression, trouble concentrating and paranoia were all found to be heritable. These findings suggest that within this population that cannabis use and dependence, as well as individual cannabis dependence symptoms have a significant heritable component, that cannabis dependence is more likely to occur when use begins during adolescence, and that the cannabis dependence syndrome includes a number of heritable untoward psychiatric side effects including withdrawal.

Figure 1

The following graphs exhibit the cumulative survival rates between two groups of subjects: those who first used cannabis under age (13,15,17,19,21,25) group (♦) versus those whose first used cannabis over age (13,15,17,19,21,25) group (◊) respectively. The cumulative survival rate is the proportion of subjects within the group who survives (i.e. not developing cannabis dependence) at different points in time after the subjects’ first exposure to cannabis. The survival curves of the older cannabis consumption group (◊) are consistently above those of the younger group (♦), and their survival curves diverge farther and farther apart as time progresses. These graphs clearly indicate that subjects that use cannabis at a later age are more likely to survive without cannabis dependence than those consume at an earlier age.