Substance abuse is the harmful use of and dependence on a drug or other mood-altering compound, whether natural or synthetic. Substance abuse is often used interchangeably with the term drug abuse. Nearly 25 million Americans were illicit drug users in 2013, according to the National Survey on Drug Use and Health, published in 2014. That report also showed that an estimated 21.6 million Americans ages 12 and older had a substance use disorder in the previous year, meaning an addiction to drugs or alcohol. Commonly abused substances include not just illicit drugs, but also some prescription medications, such as opioids (like oxycodone and hydrocodone), stimulants (such as cocaine and dextroamphetamine) and depressants (including benzodiazepines and barbiturates). These drugs may at first be prescribed for medical reasons and a person later takes the medication in a way that wasn’t prescribed, or illegally takes a medication without a prescription. Still others become addicted to over-the-counter medications like cough or cold syrups and sleeping pills that are readily available, legal drugs. Other commonly abused drugs include hallucinogens, inhalants, sedatives, hypnotics, cannabis (marijuana, for non-medical purposes), alcohol and tobacco.