WHY IT MATTERS: Patients using cannabis to manage sleep should understand that poor sleep and impulsive substance use can reinforce each other in a cycle that is harder to break than either problem alone. CLINICAL OVERVIEW: Sleep deprivation does not simply make people tired; it measurably shifts decision-making toward impulsivity, which has direct consequences for substance use behaviors including cannabis and alcohol. When the brain is under-rested, the prefrontal cortex loses some of its regulatory grip over reward-seeking circuits, lowering the threshold for risky choices.