Depression and Cannabis Use May Share Brain Reward Processing Deficits, But Evidence Is Inconsistent

Across 46 articles, brain regions most frequently associated with anhedonia across neuroimaging studies were the anterior cingulate cortex, nucleus accumbens, and medial prefrontal cortex, which are the same regions implicated in cannabis-related reward processing deficits. However, no biochemical marker (including IL-6 and CRP) was consistently associated with anhedonia, and only 2 articles specifically examined amotivation in cannabis use. Study designs and anhedonia measures were highly heterogeneous.

Systematic review searching 8 electronic databases. Included original research on biological factors or behavioral tasks associated with anhedonia in depression (44 articles) or amotivation in cannabis use (2 articles). PROSPERO-registered.

The neurobiological overlap between depression-related anhedonia and cannabis-related amotivation could inform shared treatment approaches. Understanding these deficits in adolescents may be particularly important given the co-development of mood disorders and cannabis use during this period.

The "amotivational syndrome" long attributed to cannabis use and the anhedonia of depression may share common neurobiological roots in disrupted reward processing. Identifying shared mechanisms could unlock treatments that address both conditions simultaneously.

Overwhelmingly focused on depression (44 studies) vs cannabis (only 2 studies). Heterogeneous study designs prevent quantitative synthesis. Most anhedonia measures were self-report. Small sample sizes in many included studies. Cannot determine if shared brain regions reflect shared pathology or coincidental overlap.