Historically, addiction has been defined with regard solely to psychoactive substances (for example alcohol, tobacco and other drugs) which cross the blood-brain barrier once ingested, temporarily altering the chemical milieu of the brain.

Many people, both psychology professionals and laymen, now feel that there should be accommodation made to include psychological dependency on such things as gambling, food, sex, pornography, computers, video games, internet, work, exercise, idolising, watching TV or certain types of non-pornographic videos, spiritual obsession, cutting and shopping so these behaviors count as 'addictions' as well and cause guilt, shame, fear, hopelessness, failure, rejection, anxiety, or humiliation symptoms associated with, among other medical conditions, depression and epilepsy Read More

Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. 

The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts. The terms have a huge range of definitions related to taking a psychoactive drug or performance enhancing drug for a non-therapeutic or non-medical effect. All of these definitions imply a negative judgment of the drug use in question (compare with the term responsible drug use for alternative views).

Some of the drugs most often associated with this term include alcohol, amphetamines,barbiturates, benzodiazepines, cocaine, methaqualone, and opioids. Use of these drugs may lead to criminal penalty in addition to possible physical, social, and psychological harm, both strongly depending on local jurisdiction. 

Other definitions of drug abuse fall into four main categories: public health definitions, mass communication and vernacular usage, medical definitions, and political and criminal justice definitions.

Worldwide, the UN estimates there are more than 50 million regular users of heroin, cocaine and synthetic drugs.

  Close