The role of coping in the association between cannabis use disorder and mental health; a one-year prospective study

Background: Cannabis use and cannabis use disorder (CUD) are associated with mental health problems, including depression, anxiety, but also early life trauma (ELT). CUD symptoms may be exacerbated if one uses cannabis to cope with mental health problems. Although various studies examined the role of coping in the associations between mental health problems and cannabis use, studies in individuals with a diagnosed CUD are lacking. We investigated the association of ELT, anxiety, and depression with CUD severity and amount of cannabis use, including the potential moderating role of coping in these associations in individuals with CUD. Furthermore, one-year follow up assessments were included to determine if baseline ELT, anxiety, or depression were associated with escalation of use and whether coping motives moderated escalation.
Methods: A total of 81 participants with CUD and 63 matched controls (18-31 years old) from the Netherlands completed an online survey assessing coping motives for cannabis use (coping subscale of the Marijuana Motives Measure), depression symptoms (Beck Depression Inventory), trait anxiety (trait subscale of the State-Trait Anxiety Inventory), and ELT (Early Life Trauma Inventory). Cannabis use was measured as self-reported grams per week during the last year. CUD symptoms were assessed with a semi-structured interview from the Mini International Neuropsychiatric Interview. At one-year follow up, CUD symptoms, grams/week, depression and anxiety scores were assessed again. 
Results: At baseline, ELT did not differ between CUD and controls, but depression (p<0.001) and anxiety (p=0.008) scores were higher in CUD than in controls. In the CUD group, anxiety (p=0.014) and depression (p=0.002) were positively associated with CUD severity, but not with grams per week. Coping moderated the association of ELT (p=0.008), depression (p=0.02), and anxiety (p=0.015) with grams per week, with higher coping being associated with a stronger positive association between mental health problems and grams per week. Interestingly, coping moderated the effects of depression (p=0.041) on CUD symptoms, unexpectedly showing that the positive association between depression and CUD was stronger in those with less coping motives. Depression, anxiety, and ELT did not predict (de-)escalation of use or CUD, and coping did not act as a moderator in these associations.
Conclusions: Although using cannabis to cope was associated with more cannabis use in those with mental health problems, it was not associated with escalation of use or an increase in CUD severity. Anxiety and depression did predict CUD severity. Contrasting our hypothesis, those with lower coping motives showed a stronger link between depression and CUD severity. This indicates that cope motives may not be a stand-alone risk factor for CUD, but part of a larger pattern of mental health factors associated with escalation of cannabis use.