Addiction and Habituation (Encyclopedia of Public Health)
Although there is no definition of "addiction" that is universally accepted, in general, addiction refers to a physiological and psychological dependency on a drug. While some drugs of abuse induce physiological addiction, others do not. Alternatively, some drugs that are physiologically addictive generally are not abused (e.g., caffeine). Tolerance to drug effects, and withdrawal symptoms upon abrupt cessation of use, which develop over time, are characteristic features of physiological addiction. "Habituation" is the term used to refer to psychological dependence on a drug. Some drugs of abuse are highly rewarding because of their influence on reinforcing neurobiological processes, but they do not necessarily result in "tissue" related withdrawal symptoms. Cessation of such drugs may lead primarily to subjective craving due to previous drug conditioning (perhaps true of some marijuana users) and craving may be more readily evoked or deeply conditioned among some persons than others ("addictive personalities"). Primary methods of assessment of addiction and habituation are completed through clinical interviews or self-report surveys (e.g., American Psychiatric Association DSM-IV, World Health Organization ICD-10). Treatment paradigms for the cessation of addiction begin with initial detoxification or withdrawal, followed by inpatient or outpatient program participation (e.g., 12-step programs, milieu, cognitive-behavioral, or behavioral). Pharmacological efforts (e.g., methadone maintenance) may be used as harm-reduction strategies among those who seem unable to quit drug use.
It is estimated that approximately 15 percent of the world's adults have serious substance abuse problems (not including nicotine addiction), and that this percentage has remained fairly constant over the past twenty-five years. Of these substance abusers, about two-thirds abuse alcohol and one-third abuse other substances, mainly marijuana, amphetamines, cocaine, and heroin. Approximately2.5 percent of the population abuse marijuana, 0.5 percent abuse stimulants, 0.3 percent abuse cocaine or opioids (such as heroin), and up to 0.8 percent abuse other substances (e.g., inhalants, depressants, hallucinogens). Sites of drug production and manufacturing, and distribution routes, tend to identify regions at high risk for abuse.
Drug abuse causes significant health-related consequences and financial losses to legitimate economies. The financial cost to society is estimated to be approximately $600 billion per year worldwide. This does not include the cost of nicotine abuse, which, through its influence on heart disease, lung cancer, chronic obstructive lung disease, and numerous other consequences, is the number one behavioral killer of people worldwide. Drugs of abuse are also associated with the production of psychotic symptoms (e.g., paranoid ideation) and with injuries due to accidents and violence. Approximately 50 percent of automobile fatalities involve alcohol-impaired drivers, and many auto crashes also involve chronic marijuana or amphetamine users.
In addition, each drug class is associated with a unique set of potential consequences. Some drugs of abuse are likely to have lethal consequences (e.g., opiates and depressants), and some have a high potential for addiction. Health consequences can also vary by drug. For example, depressants, PCP, stimulants, steroids, and cannabis are associated with cardiovascular diseases. Stimulant use is linked to seizure, digestion problems, and lung problems. Documented consequences of marijuana use include lung damage and short-term memory problems. Dementia, seizure, memory impairment, central and peripheral nervous systems impairment, gastrointestinal diseases, and cancers of the gastrointestinal tract are all consequences of alcohol consumption. Steroid use is associated with high blood pressure, potential heart attacks, liver tumors, transient infertility, and tendon degeneration. Inhalants are well-known causes of kidney, brain, and liver damage.
The development and maintenance of the addictive process involves multiple pathways and levels of influence within biological, psychological, and sociological domains. Influences exogenous to the individual include environmental, cultural, and social factors. Cultural and social norms, variations in drug use practices, and the values and behaviors of parents, siblings, friends, and role models can all affect an individual's drug experiences. Processes contributing to individual differences in substance use include physiological susceptibility, as measured in genetics studies; affective states; personality; and cognitionncluding expectancies and memory processes. Substance abuse versus substance use is more strongly related to intra-personal processes (e.g., self-medication for emotional distress) than social processes, although both are influential in the addictive process.
SUBSTANCE ABUSE AND DEPENDENCE
Substance use pertains simply to the use of a drug. Substance misuse means using a drug for a purpose or in a manner in which it was not intended or prescribed. Substance abuse is marked by an accumulation of negative consequences resulting from drug use. Substance use that leads to a decreased level of performance in major life roles, or to dangerous actions, legal problems, or social problems, indicates abuse. Substance dependence is a more severe form of drug abuse that also includes tolerance (the need for markedly increased amounts of the substance to achieve the desired drug effect), withdrawal symptoms when stopping substance use, unpredictability of substance use, and an inability to control the use of a substance to the point that it consumes one's daily life.
Withdrawal symptoms vary from drug to drug. For example, withdrawal from alcohol, sedatives, or anxiolytic agents may involve autonomic reactivity, hand tremor, insomnia, nausea or vomiting, transient illusions or hallucinations, psycho-motor agitation, anxiety, and grand mal seizures. Amphetamine or cocaine withdrawal can include fatigue, unpleasant and vivid dreams, insomnia or hypersomnia, increased appetite, and psychomotor retardation or agitation. For substance abusers, withdrawal is often a difficult process with numerous symptoms, while abstaining from drug use can lead to recovery from physical and psychological problems and an improvement in overall health.
THE DRUG ABUSE CONTINUUM
Conceptually, substance abuse can be seen as a continuum, with individuals at one end being relatively "disease-free" but engaging in maladaptive behaviors over which they have some control. These individuals may repetitively use drugs, and over time they may abuse drugs. They choose to live a certain lifestyle in which their maladaptive behavior may or may not result in other disease states associated with use (e.g., cirrhosis of the liver). If these individuals stop this negative cycle they can, perhaps on their own, learn alternative coping mechanisms and self-efficacy. Individuals at the other end of the continuum, however, seemingly have no control over their use. Some individuals appear to lose control the first time they use drugs. For these individuals drug use is like a toggle switch that is either on or off. For them, total abstention is the only alternative because they have no control processes once the switch is turned on. They may use until they die unless someone else can turn their switch off and keep it off. There is no logic to this behavior, and no choice. Users of this type will often ruin their own lives and the lives of those around them in their drive to use their drugs of choice. It seems that as one moves toward a more "at-risk" end of the continuum there is less and less control over substance use.
It is unclear what causes the difference in loss of control among those at different points of the continuum. Researchers do not understand the process very well. They do know that other factors may exacerbate the process, including biologically based differences in metabolic processes, different levels of susceptibility to the reinforcing effects of drugs, personality disorders or depression, and an inability to tolerate frustration or emotional discomfort. Some processes are under individual control, but many are not, and it does appear that the less control the individual has over these types of processes, the more likely he or she is to fall into substance abuse.
STAGES OF ALCOHOLISM AND DRUG ABUSE
During the early stages of substance abuse, the alcoholic or drug abuser experiences increasing tolerance and use. Substance use at this stage is generally for purposes of self-medication. In the later stages of abuse, life becomes centered around obtaining, using, and recovering from drug use. Loss of control, ethical deterioration, and noticeable withdrawal symptoms ensue. It is unclear, however, whether such a progression is inevitable.
In a 1991 empirical review of the study of progression in alcoholism, Jill Littrell found that approximately 60 percent of adolescent problem drinkers remit to nonproblematic levels of drinking when they reach their 20s, and that 25 percent of young adults remit to nonproblematic levels of drinking before they reach age 35. Studies examining data on adult alcoholics who have undergone a variety of treatments as inpatients and outpatients during follow-up periods of up to fifteen years provide a general profile of outcomes. Between 25 and 35 percent remain abstinent, whether or not they continue treatment. An additional 15 to 25 percent will be abstinent most of the time, with some lapse periods. Approximately 6 to 9 percent will become nonproblematic or controlled drinkers (particularly those who were lighter drinkers and suffered fewer negative consequences while drinking). Another 20 to 33 percent become stable problematic drinkers, while 15 to 25 percent will die from alcohol-related causes.
It is uncertain whether drug abusers follow a progression similar to that of alcoholics. There probably is some validity to a notion of progression for drug use in general, but more longitudinal studies are needed in this area. It is possible that such a progression might simply express the accumulation of consequences one endures each time one takes a chance by drinking or using drugs. As opposed to the stages outlined above, a substance abuser may simply incur more problems over time, along with an increased tolerance for alcohol or other drugs of abuse.
(SEE ALSO: Abstinence; Alcohol Use and Abuse; Behavior, Health-Related; Cocaine and Crack Cocaine; Drug Abuse Resistance Education [DARE]; Marijuana; Medications Abuse, Elderly; National Institute on Drug Abuse; Smoking Behavior; Smoking Cessation; Substance Abuse, Definition of)
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