Substance use disorder, also known as drug use disorder, is a condition in which the use of one or more substances leads to a clinically significant impairment or distress. Although the term substance can refer to any physical matter, 'substance' in this context is limited to psychoactive drugs. Substance Use Disorder refers to the overuse of, or dependence on, a drug leading to effects that are detrimental to the individual's physical and mental health, or the welfare of others.