This term is used to describe a phenomenon in which a drug user becomes psychologically and emotionally dependent on the use of a given drug; typically after a period of regular use. This form of dependence often contributes to a behavioral pattern of drug seeking and habitual drug use.
|The limbic system acts as the evolutionary drive of humans|
and other mammals. It drives instinct and facilitates learning
The biological mechanism underlying addiction to drugs is but one of multiple components contributing to what is predominantly a behavioral phenomenon of habitual drug use; It is important to note that the biological components to addiction discussed herein serve as an associative, influential or predispositional factor rather than a causative factor. After all, humans are not robots devoid of intelligence and free will.
Use of many if not most addictive drugs results in 2 pharmacological responses:
1) the subjective perception of the drug itself and its primary CNS/physiological effects, whether they be stimulating, sedative or hypnotic, analgetic, dissociative or psychedelic.
2) an increase in dopaminergic firing throughout the limbic structures of the brain; also known as the pleasure centers or reward, reinforcement & learning pathways. Note: dopaminergic activity in the limbic regions modulates positive reinforcement, negative reinforcement, and perceptual-memory connections. It therefore modulates the general phenomena of memory and learning.
Note: It is very important to keep in mind, even the most potentially addictive drugs do not inevitably produce pleasure. A large portion of those who simply try psychoactives, or repeatedly take psychoactives, for any purpose, find the effects unappealing or undesireable. For instance, most individuals report opioids simply making them drowsy or nauseated.
On the role of reinforcement:
The result of #2 is largely dependent on one's subjective perception of the drug-effects. Reinforcement can be positive or negative, depending on whether one perceives the effects of a drug as pleasurable, aversive, or perhaps neutral. The users' perception of the drug (1) dictates whether he is taught through reinforcement (2) to seek the drug, or to avoid the drug, in the future.
When one finds the experience aversive, there is typically no point in repeating the experience again - with the exception of treating a medical condition - and no desire to repeat the experience again.
When one finds the effects particularly pleasant, the associated positive reinforcement can lead to a desire for repeating the experience, whether it be right away or at another time - as you can already see, while the phenomenon that is known as "addiction" is supposedly driven by biochemical changes in the brain; there are, in reality, so many factors in this process that are completely subjective to ones own decision making and ones own behavior. This is exactly the problem with pathologizing a phenomenon which is diagnosed merely on the basis of behavior.
When the latter subject repeatedly uses the drug, his limbic system continues to reinforce this behavior positively, eventually teaching him to continue repeating the experience. Such drug use is a LEARNED behavior, in the same way that evolutionary behaviors are learned - sex and reproduction, the struggle for food, water, or shelter. Drug use is not the only non-evolutionary behavior learned & reinforced through this process; other hedonistic behaviors are learned this way as well, including but not limited to masturbation, comfort-eating, gambling, excercizing, socializing, falling in love, kissing, shopping, skydiving.
Continued use of the drug (or continuation of such other aforementioned hedonistic behaviors), not to mention all environmental & sensory stimuli which have become associated with the use of this drug (including and perhaps especially, its pharmacological effects), over time become wired into the instinctual or evolutionary drive. This here is the biological component referred to when addiction, or the popular "addicted brain" scans, are spoken about. These behaviors become prioritized and desired behaviors - meanwhile the unique personal manner in which an individual responds to this phenomenon is completely subjective, distinct.
Drug use is never involuntary:
The neurobiological component of addiction can make it very difficult to change such behaviors, even if they've become self-destructive. After all, they've been prioritized. However as I have emphasized and will continue to emphasize, this is not to say that the dependent subject has no control over this behavior - he does. It is partially true that the "brain" believes that the drug is essential to survival or evolution; however, this pertains strictly to the instinctual drive rather than the higher, rational, brain. Opioid addicts (or those addicted to other drugs) have every bit as much control over their drug-desires as they do over their sexual desires. Our human civility, motivation, and intelligence (all of which by the way have just as much neurobiological basis as our cravings or instincts) are the forces which restrain us, keep us from acting on primitive sexual or survival impulses and other animalistic behaviors, not to mention our hedonistic drive.
The important distinction between behavior and biology:
Meanwhile, as I stated earlier, drug induced reinforcement can be positive or negative. The
pharmacological effects produced by a drug are but one of many sensory/environmental/experiential factors with which our limbic brain associates with the behavior of drug taking. If one can understand this concept, one will understand the important distinction between behavior and biological disposition; that which distinguishes drug related brain changes with the act itself of seeking, obtaining, and using drugs, all which in modern discourse have been wrongfully classified as inexorable from brain chemistry.
Schaler makes a great analogy with alcoholism & chronic smoking - drinking is a behavior, while cirrhosis of the liver is a disease; smoking is a behavior, while lung cancer is a disease. Drinking is not cirrhosis and smoking is not lung cancer. Unless we're ready to consider the pathological desire for drugs itself to be a disease, we cannot accurately classify drug dependence as an illness.
As for whether the neurobiology itself is an illness is different debate altogether - however being that the neuropathology of eating, romance, sex and reproduction is not considered a disease; one cannot logically describe the neuropathology of drug addiction - which is conceptually and biologically identical to that of the aforementioned behaviors - to be an illness either.