Drug addiction, or dependency is the compulsive use of drugs, to the point where the user has no effective choice but to continue use. This phenomenon has occurred to some degree throughout recorded history (see "opium"), though modern agricultural practices, improvements in access to drugs, and advancements in biochemistry have exacerbated the problem significantly in the 20th century with the introduction of purified forms of active biological agents, and with the synthesis of hitherto unknown substances, such as methamphetamine and gamma-hydroxybutyrate (GHB). While "addiction" has been replaced by "dependency" as a clinical term, the terms are used interchangeably here.
The addictive nature of drugs varies from substance to substance, and from individual to individual. Drugs such as codeine or alcohol, for instance, typically require many more exposures to addict their users than drugs such as heroin or cocaine. Likewise, a person who is psychologically or genetically predisposed to addiction is much more likely to become dependent.
It is interesting to note that psychologists do not classify hallucinogens like LSD and psilocybin as addictive drugs. Experts on addiction say that the use of these drugs causes neither psychological nor physical dependency. This view is likely to change as more and more anecdotal evidence emerges of psychological addiction to recreational psychedelics such as MDMA (Ecstasy) and Ketamine.
Drug addiction has two components: physical dependency, and psychological dependency. Physical dependency occurs when a drug has been used habitually and the body has become accustomed to its effects. The person must then continue to use the drug in order to feel normal, or its absence will trigger the symptoms of withdrawal. Psychological dependency occurs when a drug has been used habitually and the mind has become emotionally reliant of its effects, either to elicit pleasure or relieve pain, and does not feel capable of functioning without it. Its absence produces intense cravings, which are often brought on or magnified by stress. A dependent person may have either aspects of dependency, but often has both.
The basis for addiction
Scientists have long accepted that there is a biological basis for drug addiction, though the exact mechanisms responsible are only now being identified. It is believed that addictive substances create dependence in the user by changing the brain's reward functions, located in the mesolimbic dopamine system—the part of the brain that reinforces certain behaviors such as eating, sexual intercourse, exercise, and social interaction. Addictive substances, through various means and to different degrees, cause the synapses of this system to flood with excessive amounts of dopamine, creating a brief rush of euphoria more commonly called a "high".
Although the high may last only a few minutes, it also produces more longer-lasting effects in the brain. Dopamine signals occurring normally in the reward system (traveling from the ventral tegmental area to the nucleus accumbens) lead to the activation of proteins designed to calm the initial reaction and foster a continued desire to pursue the behavior responsible. Addictive substances create a greater than normal dopamine release, and the subsequent reactions of the brain are greatly exaggerated as well. The amygdala, hippocampus, and frontal cortex associate the use of the drug with intense pleasure and well-being; an association that is strengthened with each exposure, and which over time comes to dominate normal thoughts and desires. When cravings for the drug are no longer controllable, the user is considered addicted. (For a contrary view of drug addiction, see Rat Park.)'
The chemicals responsible
The CREB protein, a transcription factor activated by cyclic adenosine monophosphate (cAMP) immediately after a high, triggers genes that produce proteins such as dynorphin, which cuts off dopamine release and temporarily inhibits the reward circuit. In chronic drug users, a sustained activation of CREB leaves the user feeling depressed and dissatisfied, and unable to find pleasure in previously enjoyable activities, often leading to a return to the drug for an additional "fix". It also leads to a short term tolerance of the substance, necessitating that a greater amount be taken in order to reach the same high.
Another transcription factor, known as delta FosB, is thought to activate genes that, counter to the effects of CREB, actually increase the user's sensitivity to the effects of the substance. Delta FosB slowly builds up with each exposure to the drug and remains activated for weeks after the last exposure—long after the effects of CREB have faded. The hypersensitivity that it causes is thought to be responsible for the intense cravings associated with drug addiction, and is often extended to even the peripheral cues of drug use, such as related behaviors or the sight of drug paraphernalia. There is some evidence that delta FosB even causes structural changes within the nuclear accumbens, which presumably helps to perpetuate the cravings, and may be responsible for the high incidence of relapse that occur in treated drug addicts.
Mechanisms of effect
The mechanisms by which different substances activate the reward system vary among drug classes.
- Stimulants such as amphetamines and nicotine increase dopamine signaling, either by directly stimulating its release, or by blocking its absorption (see "reuptake"). These substances (sometimes called "uppers") typically cause heightened alertness and energy.
The most common drug addictions are, in fact, to legal substances such as:
Many prescription or over the counter drugs can become addictive if abused. Steroidal medications, for example, are extremely addictive. In addition, a large number of other substances are currently considered to have no medical value and are not available over the counter or by prescription. Depending on the jurisdiction, these drugs may be legal only as part of a government sponsored study, illegal to use for any purpose, illegal to sell, or even illegal to merely possess.
In 1972, United States President Richard Nixon declared a war on illegal drugs in an attempt to control the growing problem of drug addiction and drug-related crime. It is unclear, though, whether laws against drugs do anything to stem usage and dependency. In jurisdictions where addictive drugs are illegal, they are generally supplied by drug dealers, who are often involved with organized crime. Even though the cost of producing most illegal addictive substances is very low, their illegality combined with the addict's need permits the seller to command a premium price, often hundreds of times the production cost. As a result, the addict must often turn to crime to support his habit.
Recovery from drug addiction
Methods of recovery from addiction to drugs vary according to the drugs involved and the needs of the individual. The 12 Step recovery programs are commonly known and used for a variety of addictions. Substance-abuse rehabilitation (or "rehab") centers usually offer a residential treatment program for the seriously addicted in order to isolate the patient from drugs and interactions with other users and dealers. Outpatient clinics usually offer a combination of individual counseling, group counseling, and prescriptions to drugs such as methadone. Although methadone is itself addictive, opium dependency is often so strong that the gradual tapering of a less-addictive substance is the only way to reliably treat the user. Other treatments, such as acupuncture, may be used to help alleviate symptoms as well.
Drugs known to be addictive
- Nestler, Eric and Malenka, Robert (Mar. 2004). "The Addicted Brain". Scientific American, pg. 78-83.
- Leavitt, Fred (2003) The REAL Drug Abusers. Rowman & Littlefield.