Substance abuse is a recognized medical brain disorder. It refers to the abuse of illegal or legal substances. Alcohol is the most common legal drug of abuse. Substance dependence describes abuse of drugs or alcohol that continues, even when serious problems related to their use have developed.

Genetics can play a part in whether you have problems with alcohol. But many other factors also have an influence. Here's what you should know.

Three kinds of prescription medicines are potentially addictive: opioids, tranquilizers, and stimulants. Here's what you should know.

Knowing about marijuana can help you tell if your child or someone else is using it, and help them to get treatment.

Cocaine use ranges from once in a while to nonstop. There is no safe way to use the drug.

Learn more about GHB, a dangerous and addictive illegal drug. GHB produces a feeling of euphoria and hallucinations. It is popular with teens who go to all-night dance parties.

LSD, also called acid, is one of the most commonly used hallucinogens or psychedelic drugs.

Until recently, heroin was not considered a problem among children of middle-class parents. But lately, it has been showing up in new places. Today the typical user could be a person from any race, part of the country, socio-economic level, or age.

Methamphetamine (meth) is a highly addictive drug. It is related to the legal stimulant amphetamine, but has stronger effects.