Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users

Area of Science:

• Neuroscience
• Psychopharmacology
• Addiction Research

Background:

• Cannabis is the most prevalent drug in the EU, followed by cocaine.
• While cannabis impairs neurocognition in occasional users, heavy users may develop tolerance.
• Understanding these effects in heavy users is crucial for addiction research.

Purpose of the Study:

• To assess the range of neurocognitive functions affected by Δ(9)-tetrahydrocannabinol (THC) in heavy cannabis users.
• To determine if THC impairments are widespread or domain-specific in this population.
• To evaluate the acute effects of cocaine on heavy cannabis users' neurocognition.

Main Methods:

• A double-blind, placebo-controlled, three-way crossover study.
• 61 heavy cannabis users with a history of cocaine use participated.
• Administration of single doses of cocaine HCl, cannabis (THC), and placebo, followed by neuropsychological testing.

Main Results:

• Cannabis (THC) impaired psychomotor function and increased impulsivity task errors.
• Cocaine improved psychomotor function but increased errors and decreased response time in impulsivity tasks.
• Observed THC impairments were less pronounced in heavy users than previously reported for occasional users.

Conclusions:

• Heavy cannabis users exhibit widespread neurocognitive impairments under THC intoxication.
• Tolerance may reduce the magnitude of THC's effects on psychomotor and impulsivity tasks in heavy users.
• Heavy users are sensitive to cocaine's stimulant and inhibitory effects, potentially increasing addiction risk.