Genetic and Environmental Factors in Addiction

The _nature versus nurture_ debate is one of the central questions which modern science is trying to answer. The question arises as to why some people become addicted to alcohol and drugs, but others do not.

_Nature versus nurture_ is the phrase used to describe this debate in developmental psychology and physiology. However, it is just as important in questions about adults. As a person’s genes are beyond their control and are determined through natural processes, the term _nature_ generally refers to genetic influences upon people.

Since adults generally live separately from their parents, the term _nurture_ doesn’t apply to them. However, the term can broadly be understood as the various external influences upon the individual due to the environment in which they live. Environmental factors could include the way people were raised by their parents, their socioeconomic status, their peer group or their situation at work, among numerous other influences from the outside world.

Public Policy and Addiction Treatment

The vital question is how much of behavior is influenced by genes and how much by the environment. The answer to this question is extremely important from a policy standpoint. Take the problem of addiction to alcohol. If it turns out that the environment is more important than genetics in causing addiction to alcohol, the best way to deal with this problem would be to regulate the environment.

Most governments regulate the sale and consumption of alcohol in some way, and this effectively regulates the environment in which people live. People younger than a certain age are restricted from drinking alcohol in most countries. Some countries enforce a high tax on alcohol to discourage people from using it.

If the environment plays an important role in addiction to alcohol, rehabilitation programs and other interventions can then play an important role in recovery. During these programs, clients usually live in controlled environments where they cannot access alcohol and where they can get involved in many other activities rather than drinking. Counselors teach clients how to control their environment after they leave rehab, perhaps by avoiding social situations where they would be expected to drink or by eating at restaurants where alcohol isn’t served. This helps them to avoid relapse.

If it turns out that genetic factors are most important in addiction, then the best way to deal with addiction would be different in some ways. Some people may have a genetic predisposition to become addicted to alcohol. Their nervous system may react strongly to the substance, thus causing a comparatively large release of hormones such as dopamine. Dopamine is integral to the reward pathways inside the brain, and when a particular activity causes dopamine to be released then people feel good and wish to repeat that activity. Another way that genetics could make someone predisposed to alcohol abuse is if they tend not to get [hangovers]( from drinking too much.

If genetics plays the more important role, it could be more effective to focus on treatments that deal directly with the genes involved in addiction. Medicines could be developed that would block the release or uptake of dopamine by the nervous system. Some pharmaceutical firms have already released pills that will make someone feel sick if they drink alcohol. These interventions are targeted more at the hormones and neurotransmitters in the body than at external environmental factors.

Genetic Influences on Addiction

Studies have found that genes are responsible for a significant part of the probability that someone will become addicted to any kind of substance or behavior. It should be noted that there is no such thing as a gene for alcoholism or a gene for cocaine addiction. Numerous genes are involved in substance addiction.

While [genetic influences]( are generally significant factors in addiction, they play a larger role in addiction to some substances or behaviors. Genetic influences appear to account for about half the risk of becoming an alcoholic, though the genetic link seems to be stronger between fathers and sons. [Addiction to cocaine]( or heroin appears to be [more influenced by genetics]( than alcoholism, while [addiction to marijuana]( appears to be less so.

Some genetic factors may make someone more likely to become addicted to only one specific drug. For example, certain genes may make some people [less likely to get a hangover]( after drinking large amounts of alcohol. Some may get an especially-large jolt of dopamine, a neurotransmitter associated with pleasurable feelings, from drinking alcohol. These genetic factors would predispose the person to become addicted to alcohol, but not necessarily to other substances.

On the other hand, some genes make people [more likely to become addicted in general]( People might have a genetic predisposition to try out novel substances. They might be genetically predisposed to thrill-seeking or risk-taking behavior, getting large spikes in dopamine through what they consider to be the excitement of drug use. They could be predisposed to keep returning to activities that they find pleasurable, despite what they may know of the potential for harmful side-effects. These genetic influences could make them more likely to become addicted to alcohol, cocaine, tobacco, gambling, or any number of substances or activities. This is known as cross-addiction.

Genes and Environment Can Be Linked

The effects of genetics and environment can often be hard to separate, and many statistics cited in the media fail to take this into account. Children of alcoholic parents are likely to inherit many of the genes that would make them predisposed to alcoholism. However, they are also more likely to grow up in an [environment that is conducive to alcohol addiction]( They are likely to see their parents, who they probably consider to be role models, drinking alcohol. Alcohol is also likely to be available in the house.

The best way to separate these genetic and environmental factors is to [study pairs of identical or fraternal twins]( raised in the same environment or in different environments. Since identical twins share all their genes, any differences between them with regard to substance addiction would seem to be the result of differences in their environments and personal experiences. Studies on alcohol addiction using twin pairs find that roughly half the risk of becoming an alcoholic is due to genetics.

Environmental Influences on Addiction

Studies find that the environment also plays a significant role in addiction. The environment in which someone grows up is important, as is the environment in which they live as adults. Someone may be encouraged to drink if they spend a lot of time with [friends who like to drink]( They may drink more if they remember having fun while drinking when they were younger. They may drink in response to [stressful factors]( in their environment, such as problems with their work or family.

The interplay between genetics and environment is complex. People who are genetically predisposed to give in to peer pressure are more likely to become addicted only if they also encounter an environment where their peers press them to drink. People who are genetically predisposed to get an intense high from cocaine are only at risk of addiction if they are in an environment where cocaine is available.

The point is that while people can’t control their genes and they can’t control some factors in their environment, there are also parts of their environment that they can regulate. By avoiding addictive substances and situations in which they are available, people can reduce the risk that they will become addicted. Even if someone has a genetic predisposition to become addicted to heroin, they will not become addicted if they never try it.

Abstinence may be a realistic approach for avoiding addiction to substances such as cocaine and heroin. However, it is less likely that people will successfully abstain from alcohol or sex. People who are susceptible to addiction to these hard-to-avoid substances or behaviors will need to find different ways to control their environment to limit their chances of addiction.

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