Substance abuse or misuse is defined as the continued misuse of any psychoactive substance that is harmful or hazardous to a person’s wellbeing health, social situation and responsibilities. People who misuse substances have difficulties controlling use and persist using despite harmful consequences and will sometimes experience a physical withdrawal state if they reduce or abstain from using. Alcohol dependence is the most common form of substance misuse, but any drug, including heroin, cocaine, crack and cannabis, comes into this category, as does the misuse of glue and aerosols and prescription medicines.