Drug addiction exhibits as a “compulsive drive to take a drug despite adverse consequences” (Volkow, N.D. & Li, T.K., 2004). It describes people who are habitual drug users, however, not all habitual drug users are addicted to drugs. Drug addicts are users who, despite the damaging effects on their health and their social life, continue to take a drug even if they’ve tried to stop. There are both biological and non-biological influences on drug addiction but a lot of the research focuses on a biological approach to addiction. Research has shown that drug tolerance can be influenced by environmental cues and that there’s other factors which influence the effects of administering drugs, as well as the probability that abstained drug users will eventually relapse. It’s important to understand addiction and the biological/non-biological justifications for substance use and abuse, as well as the reward circuits which are thought to be the foundation of substance use and abuse. This essay will look at theories of the motivations for addiction, the biological processes involved and the reasons for relapse.
Many people have the opinion that drug addicts have a physical dependency on the drug and take it to counteract any withdrawal symptoms they’re having, in turn entering a vicious circle of drug taking and withdrawal symptoms (Pinel, J. P. J., 2012). However, addicts who have undergone the detoxification process usually return to taking drugs and so there must be another reason addicts struggle to stop administering drugs. Positive-incentive theories of addiction hypothesise that most addicts take drugs to experience the positive “high”, not to counteract the unpleasant feelings of withdrawal suggest (Kennett, J., Matthews, S. & Snoek, A., 2013). It’s proposed that addiction is due to the hedonic affects that all drugs with potential for addiction have for users. Both physical-dependence and positive-incentive theories explain addiction from a biological approach. It’s also a common belief that this extreme drug taking behaviour is due to bad ‘choices’ made willingly by the addict. However, imaging studies have shown that there’s a disruption in the brain regions that are important for the normal processes of motivation, reward and inhibitory control in individuals with addiction (Volkow, N.D., et al, 2009). This evidence suggests that addicts may be suffering from a disease of the brain and their irregular behaviour may therefore, result of the damaged brain tissue. The American Society of Addiction Medicine supports this theory and has described addiction as a ‘chronic brain disease’ (Smith, D. E., 2011). The disease model of addiction therefore describes the ‘neuroplastic response’ that some addicts experience through repetitive drug administration, however, the disease theory isn’t widely accepted throughout research (Koob, G. F., & Le Moal, M., 2005).
There are many addictive drugs ranging from nicotine in tobacco to opiates that are commonly abused by addicts. The physical-dependence theory of addiction stated that drug addicts who take enough of a drug to cause a physical dependence would be driven by withdrawal symptoms to administer the drug, whenever they tried to stop taking it. With this in mind, early treatment programs were based on the physical-dependence theory and therefore, addicts were hospitalised in the hope that they could break the sequence of drug taking through gradual withdrawal. However, many drug users continued to use even after discharge even when they had no drugs left in their body. Detoxification didn’t work as a treatment because for some very addictive drugs such as cocaine, severe withdrawal symptoms aren’t produced. Without the withdrawal symptoms as the primary motivation for continuing to take drugs, the treatment doesn’t work. This theory also doesn’t explain why people start taking the drugs initially.
Positive-incentive theories of addiction were developed in response to the problems with physical-dependence theories (Higgins, S. T., Heil, S. H., & Luisser, J. P., 2004). This methodology was based on the premise that most addicts take drugs to experience the hedonic (pleasurable) effects of a drug, rather than to escape the negative effects of withdrawal (Cardinal, R. N., & Everitt, B.J., 2004; Everitt, B. J., Dickson, A., & Robbins, T. W., 2001). That isn’t to say that addicts do not regularly take drugs to ease their withdrawal symptoms, however, their primary motivation is the positive effects of the drug (Baker, T.B., et al., 2006). There are a few issues with the positive-incentive theory in that many addicts take drugs due to a high anticipation of the pleasure they will experience from taking the drug (positive-incentive value), however, often the amount of pleasure actually experienced (hedonic value) is less than anticipated. Another issue with the theory is that many people use drugs without becoming addicted to them (Everitt, B. J., & Robbins, T. W., 2005; Kreek, M. J., Nielson, D. A., Butelman, E. R., & LaForge, K. S., 2005). Therefore, it’s important to consider what causes the change from habitual drug user to drug addict. The incentive-sensitization theory of drug addiction addresses both issues. The incentive-sensitization theory suggests that in drug addicted individuals there’s an increase in positive-incentive value as their drug use also increases, meaning that the addicts have a higher motivation to find and consume the drugs (Berridge, K. C., & Robinson, R. E., 2003). This theory has important implications as it suggests that the anticipation of the pleasure from a drug is basis of drug addiction, rather than the actual pleasure experienced during administration (Robinson, T.E., & Berridge. K.C., 1993). This is because drug tolerance develops in individuals who regularly take drugs and the pleasure users get from the drug decreases with continued use. However, their craving for the pleasure increases due to this influence of a positive-incentive value in drug taking.
Drugs can be administered orally, through injection, inhalation or through mucous membranes. Once consumed, the drug enters the bloodstream where it travels to the Central Nervous System (CNS). A blood-brain barrier attempts to protect the brain by stopping many potentially hazardous chemicals which may try to pass from the CNS’s blood vessels into its neurons. Studies into the neural mechanisms of addiction have drawn attention to intracranial self-stimulation which describes the self-administration of weak electrical signals to specific sites in the brain. Olds, J., & Milner. P (1954) were the first to introduce the idea of intracranial self-stimulation and they suggested that the areas in the brain that facilitate self-stimulation are the same areas of the brain (pleasure centres) that normally control the hedonic effects of natural rewards such as food or sex (reward circuits). With this in mind, research into the neural mechanisms of addiction and their influence on drug addiction has focused on the gratifying effects of drugs. This positive effect acts as positive reinforcement to continue taking the drugs. Research has shown that dopamine plays an important role in self-stimulation, as dopamine is present in the areas of the brain where self-stimulation occurs. There’s been evidence to show that there’s an increase in dopamine levels, and therefore pleasure, after a natural reward an addictive drug has been presented to reward brain stimulation (Hernandez, G., et al., 2007). This process describes the reward circuits of the brain. Enzymes in the liver then work to neutralise the drugs; drug metabolism (Hodgson, E., & Rose, R., 2005). In most cases, drug metabolism removes a drugs ability to diffuse through the lipid membranes of cells, in turn stopping the drug from piercing the blood-brain barrier. Any drugs that do manage to penetrate the blood-brain barrier are neutralised, allowing the effects of the drug ‘high’ to subside.
Addiction is a prolonged disorder, characterised by the high probability that addicted individuals will relapse (Milton. A. L., & Everitt, B. J., 2012). The likelihood of relapsing is potentially the most difficult issue to combat when treating addicts rather than getting them to give up drugs. Therefore, understanding what causes the relapse of addicts is imperative to understand addiction and how to treat it. Shaham, Y., & Hope, B. T. (2005) found three varying causes of relapse in drug addicts. The first factor influencing relapse is stress which tends to influence people to turn to substances such as alcohol and nicotine to relax them. The second influencing factor is ‘drug priming’ which describes when a user takes a drug they had previously abused, one more time. Many addicts who have managed to refrain from taking drugs for a few weeks make the mistake of thinking that their addiction is under control. However, after taking the drug once they often end up lapsing back into their full-blown addiction. The last factor influencing relapse is an addict’s exposure to external cues that were previously associated with drug taking. There were a lot of U.S. soldiers who became heroin addicts while serving during the Vietnam War but when they returned home they were easily able to stop taking the drugs because their main environmental cue had been removed (Pinel, J. P. J., 2012). This demonstrates the effects of conditioned drug tolerance.
Conditioned drug tolerance defines the effects of tolerance which are expressed only when a drug is taken in the same situation in which it had previously been administered (McDonald, R. V., & Siegal. S., 2004). Research into conditioned drug tolerance in rats showed that the rats were only tolerant to alcohol when injected in the same situation that they had previously been administered with alcohol (Crowell, C. R., Hinson, R. E., & Siegal, S., 1981). Research has shown that there a large and reliable effect of situational specificity in drug tolerance. The fact that environmental cues have an effect on drug tolerance however, has implications for addicts in regards to drug overdose. If addicts become more tolerant to a drug each time they administer it in the same situation then they will begin to take larger doses. If then, the addict moves to a novel situation and takes the same large dose that they had administered in the normal situation, the situational effects will not be in place to counteract the effects of the drug. This means that drug overdose is more likely and so addicts are at a higher risk if taking drugs in a new environment. Siegal, S., Hinson, R. E., Krank, M. D., & McCully, J. (1982) proved this theory when more heroin-tolerant rats died when given a large dose of the drug in a new environment that their counterparts who administered the drug in the same environment as before. The development of drug tolerance is a conditioned compensatory response to drug exposure. Environmental cues also act as a conditioned compensatory response which predict drug tolerance. The same compensatory responses can be found in drug addicts who have abstained from drugs and whose cravings have worsened causing a relapse. Internal cues such as thinking about drugs can also act as conditional stimuli occasionally inducing craving in addicts and therefore a relapse.
In conclusion, drug addiction seems to have both a biological and non-biological basis. Biologically speaking, drug addiction is reinforced by reward circuits in the brain which release an increased amount of dopamine into the CNS after experiencing the drug. This is due to the pleasure centres in the brain experiencing a higher level of hedonic value with the release of dopamine. Drug addicts therefore tend to continue to administer drugs due to high anticipation of the pleasure they will receive from taking the drug, as explained in positive-incentive theories of addiction. However, the anticipation drug addicts have for the hedonic value doesn’t usually match up to the actual pleasure they experience. This leads to addicts taking a higher dosage of the drug each time they administer it. Situational effects on drug addiction shows that tolerance to a chosen drug increases if an addict administers in the same situation each time, however, the situational effect doesn’t counteract the effect of the drug in a novel environment. Situational influences therefore have implications for the drug addicts who administer in new situations. Addicts have a high chance of relapsing even if they’ve abstained from the drug for a while, perhaps due to an unstable emotional state or because they misjudged the effect of drug priming. They may feel like because they’ve abstained from the drug for a few weeks they’ll be okay to take it once, when the opposite is a reality. The theory that drug addiction is a disease defines drug addiction in terms of the changes to brain structure and performance caused by drug addiction. This view is not yet widely accepted, however, along with other research it suggests addiction isn’t purely down to biology.