The use of marijuana can impair short-term memory, verbal skills, judgment, distort perception, and impair driving performance. Heavy marijuana use impairs a persons ability to form memories, recall events, or shift attention from one thing to another. Users who have taken high doses of the drug may experience acute toxic psychosis, which includes hallucinations, delusions, and depersonalization (a loss of the sense of personal identity or self-recognition).
When smoking marijuana, THC rapidly passes from the lungs into the bloodstream. Within a few minutes an individuals heart begins beating more rapidly, the bronchial passages relax and become enlarged, and blood vessels in the eyes expand. The heart rate may increase by 20 to 50 beats per minutes. In the brain, the THC connects to cannabinoid receptors on nerve cells and influences the activity of those cells. These receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement. The effects begin immediately and can last from 1 to 3 hours. The THC in the brain causes the user to feel euphoric, by stimulating the release of the chemical dopamine. A marijuana user may experience pleasant sensations, colors and sounds may appear to be more intense, and time seems to pass very slowly. The users mouth feels dry, and he or she may suddenly become very hungry and thirsty. The hands may tremble and grow cold. The euphoria passes after awhile and then the user may feel sleepy or depressed. Occasionally, marijuana use produces anxiety, fear, distrust, or panic. THC also disrupts coordination and balance by binding to receptors in the cerebellum and basal ganglia, the parts of the brain that regulate balance, posture, coordination of movement, and reaction time.