The inclusion of multiple classes of drug users emphasizes the consistency of this visual cortex activity in substance use literature, (i.e., nicotine, alcohol, marijuana, cocaine, opiates, etc.). The generalizability of the results, however; is influenced by the disproportionately large number of studies on nicotine and alcohol. While this distribution generally reflects the historic trends in drug use and abuse in the United States (Johnston et al., 2014), there were very few available studies on marijuana or prescription opiate cue-reactivity, which are growing segments of the population.
