psychpost | 8/13/2012 08:00:00 AM
In this post I will be outlining two different theories on how drug addiction develops. Before we begin I first need to define positive and negative reinforcement.
Positive Reinforcement: The addition of a stimulus or event that will increase the frequency of a certain behavior or response.
Negative Reinforcement: The removal of a stimulus or event that will increase the frequency of a certain behavior or response.
|Why does drug use continue even after these results? source|
In these following theories of drug addiction, the behavior that is increased will be the frequency of drug use.
Negative Reinforcement Theory of Drug Addiction (Physical Dependence Model)
I chose to first begin talking about this Negative Reinforcement Theory because it was developed before the Positive Reinforcement theory and it is the theory most people are familiar with. The idea behind this theory is that every drug produces a range of certain effects, let's call them effects A, B, and C (which are usually effects that are sought after (ie euphoria). As long as the drug is being used the user will experience the effects. Because of Compensatory Changes (read my previous post for details) once the user stops administering the drug they will experience the opposite effects of ABC, let's call these X, Y, and Z (which are usually negative effects. ie dysphoria). These effects are known as withdrawal symptoms.
According to the Negative Reinforcement Theory, drug use will persist in order to alleviate these withdrawal symptoms. After the effects ABC are gone and XYZ come back, more drug is necessary to alleviate the symptoms. This cycle continues and the drug will continue to be administered.
Positive Reinforcement Theory of Drug Addiction (Incentive-Sensitization Model)
This theory focuses on the rewarding properties of dopamine in certain brain areas like the Nucleus Accumbens. One common factor of drugs that cause addiction is that they release dopamine in these areas by varying mechanisms. The idea of this theory is that dopamine release in the Nucleus Accumbens due to drugs is a process that is sensitized, meaning more dopamine gets released in after repeated use. there is experimental data showing that this actually occurs and is measured by psychomotor response (which is increased with DA release in the NA). So this leads to the drug being more rewarding for the user and increasing the "want" for the drug.
Both of these two theories offer plausible explanations on how drug addiction occurs. Removal of negative withdrawal symptoms and also the reinforcing nature of the drugs themselves can make an individual more likely to use a drug. a problem with the physical dependence theory is that there is no good relationship between strength of withdrawal and the strength of addiction. For example the withdrawal symptoms of alcohol are very severe when compared to those of heroin but heroin is far more addictive. Another problem with the physical dependence theory is that withdrawal will eventually cease but addiction still remains. The positive reinforcement theory is able to account for the difference in addictiveness (from most to least) for example: amphetamine, heroin, cocaine, nicotine, alcohol. While there are problems with the physical dependence theory, relieving withdrawal symptoms by using the drug will cause the sensitization of dopamine release causing the drug to be more rewarding according to the positive reinforcement theory.