While the genetic overlap between smoking and other forms of adolescent substance use appears to be tenuous, these links appear to be sensitive to the measures of smoking used and the comorbid drug under study. One study reported that as heritability of smoking increased, the genetic correlation between drinking and smoking also increased34. Smoking and cannabis use also share common genetic factors.51 Intriguingly, two studies have reported that cannabis initiation could be linked to smoking progression, independent of its relationship with smoking initiation 52,53.
