Addiction is a brain disorder characterized by compulsive engagement in rewarding stimuli despite adverse consequences.[8] 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.[1][9] 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., they are perceived as being inherently positive, desirable, and pleasurable).[1][3][7]

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., eating food, the use of cocaine, engagement in sexual activity, participation in high-thrill cultural activities such as gambling, etc.).[1][10][11] ΔFosB, a gene transcription factor, is a critical component and common factor in the development of virtually all forms of behavioral and drug addictions.[10][11][12][13] 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 overexpression of ΔFosB in the D1-type medium spiny neurons of the nucleus accumbens.[1][10][11][12] Due to the causal relationship between ΔFosB expression and addictions, it is used preclinically as an addiction biomarker.[1][10][12] ΔFosB expression in these neurons directly and positively regulates drug self-administration and reward sensitization through positive reinforcement, while decreasing sensitivity to aversion.[note 1][1][10]

Addiction exacts an “astoundingly high financial and human toll” on individuals and society as a whole.[14][15][16] In the United States, the total economic cost to society is greater than that of all types of diabetes and all cancers combined.[16] These costs arise from the direct adverse effects of drugs and associated healthcare costs (e.g., emergency medical services and outpatient and inpatient care), long-term complications (e.g., lung cancer from smoking tobacco productsliver cirrhosis and dementia from chronic alcohol consumption, and meth mouth from methamphetamine use), the loss of productivity and associated welfare costs, fatal and non-fatal accidents (e.g., traffic collisions), suicides, homicides, and incarceration, among others.[14][15][16][17] Classic hallmarks of addiction include impaired control over substances or behavior, preoccupation with substance or behavior, and continued use despite consequences.[18] Habits and patterns associated with addiction are typically characterized by immediate gratification (short-term reward), coupled with delayed deleterious effects (long-term costs).[19]

Examples of drug and behavioral addictions include alcoholismamphetamine addictioncocaine addictionnicotine addictionopioid addictionfood addictiongambling addiction, and sexual addiction. The only behavioral addiction recognized by the DSM-5 and the ICD-10 is gambling addiction. The term addiction is misused frequently to refer to other compulsive behaviors or disorders, particularly dependence, in news media.[20] 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.[21] Addiction is the compulsive use of a substance or performance of a behavior that is independent of withdrawal. Addiction can occur in the absence of dependence, and dependence can occur in the absence of addiction, although the two often co-occur.


Murfreesboro is a city in and the county seat of Rutherford County, Tennessee.[7] The population was 108,755 according to the 2010 census, up from 68,816 residents certified in 2000. In 2015, census estimates showed a population of 126,118.[5]The city is the center of population of Tennessee[8] and is part of the Nashville metropolitan area, which includes thirteen counties and a population of 1,757,912 (2013). It is Tennessee’s fastest growing major city and one of the fastest growing cities in the country.[9] Murfreesboro is also home to Middle Tennessee State University, the largest undergraduate university in the state of Tennessee, with 22,729 total students as of fall 2014.[10]

In 2006, Murfreesboro was ranked by Money as the 84th best place to live in the United States, out of 745 cities with a population over 50,000.[11][12]

In 1811, the Tennessee State Legislature established a county seat for Rutherford County. The town was first named “Cannonsburgh” in honor of Newton Cannon, then Rutherford County’s member of the state legislature, but it was soon renamed “Murfreesboro” for Revolutionary War hero Colonel Hardy Murfree.[13] Author Mary Noailles Murfree was his great-granddaughter.

As Tennessee settlement expanded to the west, the location of the state capital in Knoxville became inconvenient for most newcomers. In 1818, Murfreesboro was designated as the capital of Tennessee. Eight years later, however, it was itself replaced by Nashville.[14]