  Cannabis legalization has been welcomed by many U.S. states but its role in
escalation from tobacco e-cigarette use to cannabis vaping is unclear.
Meanwhile, cannabis vaping has been associated with new lung diseases and
rising adolescent use. To understand the impact of cannabis legalization on
escalation, we design an observational study to estimate the causal effect of
recreational cannabis legalization on the development of pro-cannabis attitude
for e-cigarette users. We collect and analyze Twitter data which contains
opinions about cannabis and JUUL, a very popular e-cigarette brand. We use
weakly supervised learning for personal tweet filtering and classification for
stance detection. We discover that recreational cannabis legalization policy
has an effect on increased development of pro-cannabis attitudes for users
already in favor of e-cigarettes.
