- Opiates: Opiates act by binding to a variety of receptors that can influence mood, respiration, pain, blood pressure, endocrine function, and gastrointestinal function. Heroin is the most rapidly acting of the commonly abused opioids.
- Stimulants: The most common addictive stimulants are cocaine and amphetamines. Cocaine abuse has reached epidemic levels in this country.
- Sedative–Hypnotics: Substance abuse in this category generally involves benzodiazepines. Use of a benzodiazepine at even the therapeutic dosage for a month or more can produce physical dependence (especially with alprazolam). Thus, during treatment, it is important not to discontinue the drug abruptly, which may cause a potentially fatal withdrawal syndrome.
- Anabolic Steroids: These agents are used illegally to enhance physical appearance, athletic performance, and fighting ability. Adverse effects include a variety of physical effects on the cardiovascular, hepatic, and reproductive systems and psychiatric effects including episodes of depression, mania, psychosis, delirium, and marked aggressiveness.
- Marijuana: Addictive behavior patterns occur rarely, even with heavy use of marijuana. Likewise, dangerous physical reactions are uncommon with this substance abuse; the main physiologic effects of marijuana are increased appetite and a faster heartbeat, which is likely to be a problem only for persons with cardiovascular disease. However, the drug’s possible psychological effects are still considerably concerning.
- Phencyclidine (PCP): PCP or commonly known as “angel dust” is often smoked mixed with a leaf material (tobacco, marijuana). Even extremely low doses can precipitate a schizophrenia-like psychotic state. Death may occur, usually related to external events precipitated by drug use, including homicides, suicides, and accidents.
- Hallucinogens: Also known as psychotomimetics and/or psychedelics are a diverse group of extremely potent substances that generally produce stimulation at very low doses and hallucinations, delusions, depersonalization, and unpredictable behavior at higher doses.
- Alcohol: Alcohol consumption remains a subject of considerable concern. Most abusers of illicit drugs have abused alcohol in the past or will eventually do so.
- Nicotine: Smoking kills more than 1,000 Americans every day. Because the adverse effects of smoking become manifest over decades, young people are particularly unlikely to appreciate the reasons not to smoke.
- Inhalants: Inhalant refers to the common mode of administration rather than a particular category of substance abuse. The agents used in this manner consist of a variety of inexpensive, readily available volatile substances that provide a high; they include medical anesthetic gases (ether, chloroform, halothane, nitrous oxide); industrial or household solvents (paint thinners, degreasers, solvents in glue); art- and office-supply solvents (correction fluid, solvents in marker pens); gases used in household or commercial products (butane lighters, gasoline, whipping cream dispensers, electronic equipment dusters, and cleaners, refrigerant replenishers); household aerosol propellants (as in paint, hair spray, and fabric-protector spray); and aliphatic nitrites (“poppers”). Note that smoked drugs are excluded from this category. 
[1-2] Substance Abuse – National Center for Biotechnology Information
 Diagnosis and Treatment of Drug Abuse in Family Practice – American Family Physician Monograph – National Institute on Drug Abuse
 Detoxification and Substance Abuse Treatment – National Center for Biotechnology Information
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