A common theme among every article in this issue is the overlap be- tween NMUPD, excessive drinking, and marijuana and other forms of substance use. In every investigation, nonmedical users were observed to have a history of using alcohol, marijuana, tobacco, and other psycho- active substances. Kalyanam, Katsuki, Lanckriet, and Mackey (2017)
Kalyanam, J., Katsuki, T., Lanckriet, G., & Mackey, T. K. (2017). Exploring trends of non- medical use of prescription drugs and polydrug abuse in the Twittersphere using un- supervised machine learning. Addictive Behaviors, 65, 289–295. http://dx.doi.org/10 [7]. 1016/j.addbeh.2016.08.019.