In addition to what the review tells us about the course of substance use after a first episode of psychosis, it shines a light on the limitations of our knowledge. For example, although many individuals stop drinking or using drugs after a first episode, probably due in part to the belief that their substance use is somehow related to or a cause of the psychosis, the longer-term implications of this belief are unclear. Would a person who abstains from substance use and who experiences another episode of psychosis reconsider his or her substance-using behavior? In addition, it is unclear whether assessment and diagnosis of substance use and abuse require tailoring for young adults with psychosis; research on assessment methods and measures in this population is lacking. Given the relatively recent development of effective treatment strategies for the general adult population with comorbid psychotic and substance use disorders, it is not surprising that the literature on young adults is even leaner. Critical information about how to identify young adults with psychosis who are most in need of additional treatment for substance abuse is not available.