is a medical condition characterized by compulsive engagement
in rewarding stimuli, despite adverse consequences. Despite the involvement of a number of psychosocial factors, a biological process – one which is induced by repeated exposure to an addictive stimulus – is the core pathology
that drives the development and maintenance of an addiction. The two properties that characterize all addictive stimuli are that they are reinforcing (i.e., they increase the likelihood that a person will seek repeated exposure to them) and intrinsically rewarding (i.e., perceived as being positive or desirable).
Addiction is a disorder
of the brain's reward system
which arises through transcriptional and epigenetic mechanisms and occurs over time from chronically high levels of exposure to an addictive stimulus (e.g., morphine, cocaine, sexual intercourse
, gambling, etc.). ΔFosB, a gene transcription factor, is a critical component
and common factor in the development of virtually all forms of behavioral and drug addictions. Two decades of research into ΔFosB's role in addiction have demonstrated that addiction arises, and the associated compulsive behavior intensifies or attenuates, along with the genetic overexpression of ΔFosB in the D1-type medium spiny neurons of the nucleus accumbens. Due to the causal
relationship between ΔFosB expression and addictions, it is used preclinically as an addiction biomarker. ΔFosB expression in these neurons directly and positively regulates drug self-administration and reward sensitization
through positive reinforcement
, while decreasing sensitivity
Addiction exacts a high toll on individuals and society as a whole through the direct adverse effects of drugs, associated healthcare costs, long-term complications (e.g., lung cancer with smoking tobacco, liver cirrhosis with drinking alcohol, or meth mouth
from intravenous methamphetamine), the functional consequences of altered neural plasticity in the brain, and the consequent loss of productivity. Classic hallmarks of addiction include impaired control over substances or behavior, preoccupation with substance or behavior, and continued use despite consequences. Habits and patterns associated with addiction are typically characterized by immediate gratification (short-term reward), coupled with delayed deleterious effects (long-term costs).
Examples of drug and behavioral addictions include: alcoholism
, amphetamine addiction, cocaine addiction, nicotine addiction, opiate addiction, food addiction, gambling addiction, and sexual addiction. The only behavioral addiction recognized by the DSM-5 is gambling addiction. The term addiction
is misused frequently to refer to other compulsive behaviors or disorders, particularly dependence
, in news media. An important distinction between drug addiction and dependence is that drug dependence is a disorder in which cessation of drug use results in an unpleasant state of withdrawal, which can lead to further drug use. Addiction is the compulsive use of a substance or performance of a behavior that is independent of withdrawal.