Addiction is a complex condition. People with addiction have an enormous focus on using a certain substance to the point that it takes over their life. They keep using alcohol or drugs even when they know it will cause problems. People can develop an addiction to: - Alcohol - PCP and other hallucinogens - Inhalants, such as paint thinners and glue - Opioid pain killers, such as codeine and oxycodone, heroin - Sedatives, hypnotics (sleep aids) and anxiolytics (anxiety medication) - Cocaine, methamphetamine and other stimulants - Tobacco and nicotine People with a substance use disorder have altered thinking, behavior and body functions. Changes in how the brain is wired are what cause people to have intense cravings for the drug and make it hard to stop using the drug. These substances can cause harmful changes in how the brain functions. These changes can last long after the intoxication from the drug. Intoxication is the effects of the drug, causing intense pleasure, calmness, increased senses or euphoria. Intoxication symptoms are different for each substance.