There are many different kinds of addictions, from drugs to interpersonal relationships. Although these diverse addictions vary in many ways there are common threads that bind them together. There are several theories that model addiction: genetic theories, exposure theories (both biological and conditioning), and adaptation theories. To be successful, an addiction model must blend the multidimensional aspects of addiction. It must account for regional and cultural variation, interpersonal preferences as well as hold true for the variety of addictions. In addition, a good model will describe a cycle that exists that encourages increasing use until the addiction is overwhelming and leaves the host lame. Lastly, theories must be able to describe addiction as it occurs through human experience. Although animal studies can aid in understanding behavior, results need to be carefully interpreted before they are applied to the much more complex nature of a human being.
The genetic theory of addiction, known as addictive inheritance, attempts to separate the genetic and environmental factors of addictive behavior. Studies have been done to control for environmental components to determine if genetics plays a greater role. Most studies looking at alcoholism have determined that children born from alcoholic parents who are adopted into non-alcoholic families have a three to four fold increase in the rate of alcoholism over the rest of the population. Indeed, children born and raised by alcoholic parents have an even greater rate of alcoholism. This suggests that there is some genetic predisposition to alcoholic addiction.
Though a genetic component seems likely, exactly what the gene codes for has not been elucidated. Questions arise as to whether or not it is the addictive behavior that is encoded or a biological mechanism that drives the behavior. Are there differences in the metabolism of various addictive substances that allow an individual to have varying levels of a drug in the blood stream and have a psychological experience different someone else? Is there some genetic difference that perhaps allows some to realize when an elevated blood alcohol level has been reached and transmits a message to the brain to stop drinking that others do not have? These questions have not been clearly answered and are under persistent investigation.
One aspect of inheritance that is understood is that amongst members ofparticular races. Eskimos, American Indians, and Asians, for example, are all genetically predisposed to have a deficiency in the production of acetaldehyde, an enzyme important foralcohol degradation. Genetically similar in this regard, these groups are hypersensitive to the affects of alcohol. They respond immediately and intensely to the alcohol in their system. A characteristic flushing, known as Asian flushing, ensues once higher levels of alcohol are reached. Although this metabolic process is similar in all of these races, the addictive behavior is quite different. Eskimos and American Indians have a higher rate of alcoholism than Asians and are also predisposed for other addictive behaviors such as gambling that is not seen in Asians. This has raised the question as to whether or not a single gene can encode for multiple addictive behaviors, or if the maintenance of one addictive behavior allows for other addictions to arise more easily.
Finally, the strongest correlation between addiction and genetics comes when evaluating the pattern of inheritance. All studies show that it is sons, not daughters, who most often inherit the risk of alcoholism. How much of this phenomenon has its basis in genetic is not clear. Could it be that sons model themselves more after their fathers? Or is there a sex-linked genetic mechanism at play that is contributing to this phenomenon? As research continues, the role that genetics plays in addiction will be better understood. As of yet, it is sure to be a major component of most addictions and at the very least will predispose individuals to indulge in addictive behavior.
The exposure model is based on the assumption that the introduction of a substance into the body on a regular basis will inevitably lead to addiction. The biological, as opposed to the conditioning models, believe that this is a consequence of biology. Underlying the exposure model is the assumption that the introduction of a narcotic into the body causes metabolic adjustments requiring continued and increasing dosages of the drug in order to avoid withdrawal. Although changes in cell metabolism have been demonstrated, as of yet they have not been linked with addiction. Some theorize that those drugs that mimic endorphins (naturally occurring pain killers), if used on a regular basis, will reduce the body's natural endorphin production and bring about a reliance on the external chemical agent for ordinary pain relief.
Endorphin related explanations have been associated with other forms of addiction. It has been suggested that food and alcohol can also affect endorphin levels. This could explain the craving, or the continued psychological need, for these non-narcotic substances. The argument is even stronger for those individuals addicted to running and exercise. The "runner's high" that is commonly experienced by well-conditioned athletes is likely a result of endorphin production. Nicotine has also been implicated in stimulating endorphin receptors as a basis for addiction. Schacter's (1978) view is that cigarette smokers are physically dependent on nicotine. They continue to smoke in order to maintain habitual levels of cellular nicotine so as to avoid withdrawal. Still controversial, the exposure theory, and its implications that endorphins play a role in addiction, continues to be favored by some investigators and is a focus of much research.
The basis of conditioning theories is that addiction is the cumulative result of the reinforcement of drug administration. The substance acts as a powerful reinforcer and gains control over the users behavior. In contrast to the biological models of the exposure theories, these conditioning models suggest that anyone can be driven to exhibit addictive behavior given the necessary reinforcements, regardless of their biology. The advantage of this theory is that it offers the potential for considering all excessive activities along with drug abuse within a single framework: those of highly rewarding behavior. There are many reinforcement models that have been defined including the opponent- process model of motivation and the well known classical conditioning model. Both of these models define addiction as a behavior that is refined because of the pleasure associated with its reinforcement.
There are two proposals that account for the relentless pursuit of drugs. The first is that the drug is providing an inherent, biological reward to prevent the pain of withdrawal. The second is that the experiences brought on by the drugs bring on inordinate pleasure or euphoria. These mechanisms can act independently or synergistically. In both cases, though, the primary motivation is the reinforcement of the behavior by some tremendous reward, one that is otherwise perceived to be unattainable.
Studies by Chein et al. (1964) questioned the notion that addiction is a consequence of rewarded behavior. He noted that when normal subjects were given narcotics, although they found the experience pleasurable, they did not become compulsive drug users. His work states that drugs are not inherently rewarding as one of the above proposals suggested. Furthermore, he found that a percentage of addicts actually found the initial drug experience unpleasant, but became addicted anyway. Despite these concerns, the conditioning model is well supported and emphasizes once again that addictive behavior is complex and difficult to place into a single model.
The adaptation theories include the psychological, environmental and social factors that influence addiction. Advocates of these theories have analyzed how expectations and beliefs about what a drug will do for the user influence the rewards and behaviors associated with its use. They recognize that any number of factors, including internal and external cues, as well as subjective emotional experiences, will contribute to addictive potential. They support the views that addiction involves cognitive and emotional regulation to which past conditioning contributes.
The adaptation theory has also broadened the scope of addiction into psychological realms. Investigators have noted that drug users rely on drugs to adapt to internal needs and external pressures. The research has focused on the psychodynamics of drug reliance. Ego deficiencies and other psychological deficits, including child-rearing deficits, have been implicated. Despite their importance, these social-psychological theories exist in isolation from the other theories because of their inability to merge concepts with other, more substantiated models.