Key Findings: "In conclusion, high-potency marijuana (13% although concentrations up to 40% have been observed) was shown to consistently impair executive function as assessed in the Tower of London [decision-making] task. Motor control was likewise impaired as indicated by a decrement in tracking performance in the Critical tracking task and a decrease in motor impulse control during Stop signal task performance." Impairments were most pronounced in the first 2 hours after smoking but were still measurable at 6 hours post dosing.