Some studies show that MDMA may be neurotoxic in humans. Other studies, however, suggest that any potential brain damage may be at least partially reversible following prolonged abstinence from MDMA. Major withdrawal symptoms peak between 48 and 72 hours after the last dose and typically subside after about a week; however, some individuals may show persistent withdrawal symptoms for months. Although heroin withdrawal is considered less dangerous than alcohol or barbiturate withdrawal, sudden withdrawal by heavily dependent users who are in poor health is occasionally fatal. Marijuana harms in many ways, and kids are the most vulnerable to its damaging effects. Use of the drug can lead to significant health, safety, social, and learning or behavioral problems, especially for young users. Making matters worse is the fact that the marijuana available today is more potent than ever. In 1988, about 300,000 infants were born addicted to cocaine. | 
