Addiction is a complex condition, and a variety of substances can be addictive due to their impact on the brain's reward system. Here are some commonly known addictive substances, but it's important to note that not everyone who uses these substances becomes addicted: Stimulants Cocaine and Crack Cocaine: A powerful stimulant drug . Amphetamines: Includes drugs like Adderall and Dexedrine. Methamphetamine (Meth): A highly addictive central nervous system stimulant. Nicotine: Found in tobacco products. Depressants Alcohol: Depressant that slows down the central nervous system. Benzodiazepines: Includes drugs like Valium, Xanax, and Ativan. Barbiturates: Examples are phenobarbital and secobarbital. Opioids and Narcotics Depressants Heroin: Derived from morphine. Prescription painkillers: OxyContin, Percocet, Vicodin, and others. Fentanyl: Extremely potent synthetic opioid. Morphine: Natural substance taken from opium poppy.