A substance use disorder involves using too much alcohol, tobacco or other drugs. It can also be called substance abuse, substance dependence or addiction.
Drug and alcohol misuse isn’t necessarily related to how often — or in what quantity — a person uses drugs or consumes alcohol, but the impact this has on their life. Drug or alcohol use can become a problem when it starts to affect a person’s judgement, relationships or general health and wellbeing. It can cause them to neglect other responsibilities such as school, work or family. Many people use substances such as drugs or alcohol to relax, have fun, experiment, or cope with stressors. However, for some people the use of substances or engaging in certain behaviours can become problematic and may lead to dependence. Harmful drug use is often associated with illicit drugs such as speed or heroin but prescription or over-the-counter medicines can also be used in a harmful way, as can alcohol.