Cognitive performance in young adults who endorse a cannabis use disorder

Cannabis use disorder (CUD) is highly prevalent with ∼44 million cases worldwide. CUD has been associated with compulsive use despite experiencing adverse psychosocial outcomes. Such adverse outcomes of CUD have been attributed to altered cognition - a set of mental processes that support the organisation and implementation of goal-directed behaviour. However, the evidence is mixed and limited by methodological issues including inconsistent assessment of CUD and metrics of cannabis use.

This study examined distinct domains of cognition (i.e., executive function, working memory, episodic memory, verbal reasoning, attention, IQ) in 115 participants aged 18.5 to 32.5 years. We compared performance between 83 participants who endorsed a CUD and 32 controls. We also explored whether the level of problematic cannabis use, and cannabis grams/past month was associated with cognition in CUD. All analyses accounted for alcohol/nicotine use and trait anxiety.

CUD compared to control participants showed significantly lower IQ, with a strong effect size (p < .001, d = 0.862), which was driven by lower verbal IQ, and survived adjusting for education years. There were no other significant effects of group or associations between cognition, level of problematic cannabis use, or dosage.

Altered cognition in young adults who endorse a CUD may be specific to verbal IQ. Future work is required to confirm whether these findings generalise to CUD samples across the lifespan, including the most vulnerable individuals with a CUD who are seeking or receiving treatment and that endorse comorbid psychopathologies.