One of the fascinating things about addiction and the brain is that there is no single factor that causes addiction. As we have seen, it is not purely genetic, psychological, chemical, or behavioral. Every time you learn something, there is a chemical change in your brain that causes you to remember what you learned.
Some types of learning are conscious and intentional.
Studying for a test is an example. This is called instrumental learning. An instrumental learning process that occurs when people begin to experiment with mood-altering drugs involves several tasks. The first is learning how to obtain access to the substance; then the user has to learn how to administer it and to manage its effect.
But there is another kind of learning that occurs at a more subliminal level. This is called conditioning, and it occurs when the brain learns to associate a particular effect with a certain situation.
The most familiar example of classical conditioning is the experiment involving Pavlov’s dog. Pavlov was a Russian psychologist interested in the phenomenon of learning and memory. He rang a bell every time he fed his dog, and after a while found that the dog would salivate whenever the bell was rung, whether food was present or not. This important experiment showed that an animal’s body “learned” to change its physiology based upon an environmental cue. (We cannot normally control functions like salivating, increased heart rate, sweating, or blushing, which occur in response to environmental stimuli.)
Experiments with addicts have shown that exposure to drug-related sensory cues produces changes in heart rate, pupil size, skin conductance, and the subjective feeling of craving. There is a direct correlation between the strength of these responses and the severity of the addiction.
Addicts in methadone treatment programs have reported the onset of withdrawal symptoms in response to stressful emotions. When the methadone level in the bloodstream is constant, there is no biochemical reason for the addict to be in withdrawal. In this situation the brain has apparently “learned” that motivating the addict to use - by producing symptoms of withdrawal - will lead to the sense of relief that comes from a dose of opiates, even when they are already present in the system.
Cocaine addicts routinely report that they begin craving whenever they encounter sights, smells, and sounds that were common when and where they used cocaine. In fact, cocaine addicts in treatment centers often do not experience much in the way of craving, and may come to believe that this is not going to be a problem. However, when they return home, environmental cues trigger cravings.
In a number of treatment approaches, attempts have been made to take advantage of this effect or to reverse it. Aversive conditioning was tried for a short period of time, but is currently considered ineffective and probably unethical.
In this treatment model, the addict is exposed to a stimulus that is likely to trigger craving, such as a bottle of alcohol or drug paraphernalia. When the automatic response occurs - pupil dilation, sweating, or subjective craving - a negative stimulus such as an electric shock is applied. The theory behind this approach is that the negative stimulus will become paired with the cue that triggers the craving, and therefore the strength of the addiction will be reduced. But the treatment didn’t work very well and wasn’t very popular.
Teaching addicts to deal with triggers and cravings, though, is an important part of current treatment approaches. Conditioned responses disappear over time. If, for example, Pavlov went for a long time without feeding the dog after the bell had been rung, the dog began to salivate less and less when it did ring.
We know that cravings peak in intensity and wane over a span of ten to fifteen minutes, providing that the addict does not use the drug and diverts his or her attention to something else. Drugs that are extremely addicting, like crack cocaine, produce the strongest conditioned responses and cravings. It can take a considerable period of time for these to diminish, but, if a person learns to avoid certain stimuli and stays completely abstinent, the cravings become more tolerable as they fade.
Elizabeth Connell Henderson, M.D.
Appendix A: Regulation of Addictive Substances
Appendix B: Sources of Additional Information