Embracing comorbidity: a way toward understanding the role of motivational and control processes in cannabis use disorders

Although the general public perceives cannabis as one of the less harmful illicit drugs, the past decades saw a surge in treatment demands for CUDs (UNODC, 2014). Cannabis nowadays is the primary illicit drug of concern in drug treatment services across North America, Oceania and Africa (UNODC, 2014). The low perceived harms of cannabis use are reflected in the small number of studies investigating the neurocognitive processes underlying CUDs [e.g., only 3 published functional Magnetic Resonance Imaging (fMRI) studies in individuals with a diagnosed CUD compared to controls, contrasting more than 1000 studies in individuals with an Alcohol Use Disorder]. Most studies on the mechanisms underlying cannabis abuse, including my own, investigated heterogeneous groups of chronic or heavy cannabis users with various levels of cannabis use related problems, not groups with diagnosed CUDs. Even though a substantial part of regular cannabis users will not experience any clear negative social and health consequences of cannabis, this does not imply that CUDs are less severe than other Substance Use Disorders (SUDs). The mental health issues associated with CUDs are substantial and often include comorbid psychiatric disorders including depression and anxiety (Stinson et al., 2006). Moreover, CUDs are difficult to treat and long-term abstinence is achieved by fewer than 20% (Danovitch and Gorelick, 2012). This urgently calls for a better understanding of CUDs. It is therefore time to reach out to those coping with CUDs by studying the mechanisms underneath. The goal of this opinion article is twofold: First, I want to address the strong need for neurocognitive studies in CUDs. Second, I propose that studying neurocognitive commonalities and differences between CUDs and comorbid disorders like depression and anxiety has great potential to unravel the mechanisms underlying CUDs and to eventually reveal new treatment targets.