Shortcut for examining the frequency of substance use disorders is to utilize a combination of the percentage of individuals who have drug abuse and drug dependence as defined by the DSM-IV, since no data are yet available for the frequency of substance use disorders based on the DSM-5 criteria. Combining the old drug abuse and dependence criteria yields an approximate percentage of 15% (38.6 million people as of 2011) for the U.S. population who are 12 or older who suffered from Substance Use Disorders for alcohol, tobacco, or illicit drugs in the last year (Table 1.2). For alcohol, 9.8% of last-year users met the criteria for Substance Abuse or Dependence on Alcohol. For tobacco, 32% of the population used tobacco in the last year. For cannabis, 13.9% of last-year users met the criteria for Substance Abuse or Dependence on cannabis. For cocaine, 21.1% of last-year users met the criteria for Substance Abuse or Dependence on cocaine. For heroin, 65.5% of last-year users met the criteria for Substance Abuse or Dependence on heroin.
The cost to society of drug abuse and drug addiction is prodigious in terms of both the direct costs and indirect costs associated with secondary medical events, social problems, and loss of productivity. In the United States alone, illicit drug use and addiction cost society $161 billion per year in 2011. Alcoholism cost society $223 billion per year in 2012, and nicotine addiction costs society $155 billion. In terms of health burden, alcohol and tobacco use are in the top 10 greatest risk factors for loss of years to disease and disability.
Much of the initial research into the neurobiology of drug addiction focused on the acute impact of drugs of abuse (analogous to comparing no drug use to drug use). The focus has shifted to chronic administration and the acute and long-term neuroadaptive changes that occur in the brain. Sound arguments have been made to support the hypothesis that addictions are similar to other chronic relapsing disorders, such as diabetes, asthma, and hypertension, in their chronic relapsing nature and treatment efficacy (for further reading, see McLellan et al., 2000). Current neuroscientific drug abuse research seeks to understand the cellular and molecular mechanisms that mediate the transition from occasional, controlled drug use to the loss of behavioral control over drug seeking and drug taking that defines chronic addiction.