Substance abuse refers to the harmful or hazardous use of psychoactive substances, including alcohol and other drugs. This term is used to describe a wide range of behaviors and patterns of use that can lead to physical, psychological, and social harm, including addiction, overdose, and other health problems. Substance abuse is characterized by a persistent pattern of use despite negative consequences, and can be associated with a range of risk factors, including genetic, environmental, and social factors. Substance abuse is a complex and multifaceted issue that can have a significant impact on individuals, families, communities, and societies as a whole. The World Health Organization (WHO) is one of the key organizations that works to address substance abuse and related issues, through research, policy development, and the promotion of evidence-based prevention, treatment, and support services.