WHY IT MATTERS: If you or someone you care for uses cannabis regularly and has concerns about mood, motivation, or mental health, this emerging research on reward brain circuitry underscores why timing, potency, and age of first use are factors worth discussing openly with a knowledgeable clinician. CLINICAL OVERVIEW: The endocannabinoid system plays a central role in regulating reward circuitry, and THC directly modulates dopaminergic signaling in ways that can alter how the brain anticipates and responds to rewarding stimuli. This is particularly relevant during adolescence and young adulthood, when reward-related neural networks are still developing and may be more vulnerable to disruption from exogenous cannabinoids.