Drugs can be virtually anything that changes the user's physical or psychological makeup; they can be either legal or illegal to possess. Controlled drugs and other drugs can be grouped into six categories: stimulants, depressants, hallucinogens, narcotics, marijuana, and inhalants. Stimulants make the user feel more alert. Depressants may create a feeling of exhilaration for the user in early stages of ingestion, but they actually depress the central nervous system. Hallucinogens are unique in that they are not physically addictive. Narcotics are physically addicting and emulate the effects of opium. The Drug Enforcement Administration considers marijuana to be a mild hallucinogen; its beneficial use in medicine is still under study. The use of inhalants has become popular for adolescents and others, because they are both readily available and legal to possess. However, breathing the fumes of certain household products may pose more risk of physiological damage to the user's brain than do other dangerous substances encountered on the street. Mood drugs such as Prozac have emerged for the treatment of clinical depression, but have been questioned in terms of their side effects. Other drugs such as flunitrazipan (the date rape drug) and fen-phen (a dangerous diet drug) are also being used. Photographs, charts, list of major terms used, and discussion questions