Opiates and other narcotics are powerful painkillers that can cause drowsiness, and sometimes intense feelings of well-being, elation, and excitement. These include heroin, opium, codeine, and narcotic pain medicines that may be prescribed by a doctor or bought illegally.
Stimulants are drugs that stimulate the brain and nervous system. They include cocaine and amphetamines, such as drugs used to treat ADHD (methylphenidate, or Ritalin). A person can start needing higher amounts of these drugs over time to feel the same effect.
Depressants cause drowsiness and reduce anxiety. They include alcohol, barbiturates, benzodiazepines (Valium, Ativan, Xanax), chloral hydrate, and paraldehyde. Using these substances can lead to addiction.
LSD, mescaline, psilocybin (“mushrooms”), and phencyclidine (PCP, or “angel dust”) can cause a person to see things that are not there (hallucinations) and can lead to psychological addiction.