Cocaine and methamphetamine produce elation, confidence, and sharp focus in most users. The drugs also enable long periods of physical or mental effort, but are very addictive and can cause dangerous behavior. The positive reinforcement, autonomic arousal, and behavioral effects come from the drugs’ agonist action on dopamine and noradrenaline. An SUD occurs in about half of cocaine or methamphetamine users, and in about one-third of misusers of pharmaceutical stimulants, including Adderall and Ritalin. Addiction often develops rapidly and is most likely in daily users and those who inject the drugs IV or inhale cocaine vapor. Addicts often use the drugs in binges that continue uninterrupted for days. Extreme irritability, suspicion, and social withdrawal are common. Obsessive thought patterns sometimes lead to psychotic paranoia. Clinical depression and suicide are definite risks. Heavy stimulant use damages the cardiovascular system, kidneys, and the brain, and causes impairment of memory and executive function. Withdrawal brings depression and emotional lability. Smaller, less active babies with increased emotional reactivity result from prenatal exposure to stimulants.