In the continuing search for the causes of addictive behavior, various models have been proposed, like the biological model of addiction. These are similar to theories, but instead of trying to explain addiction, a model tries to put it in a larger framework so that useful therapies can then be developed. So a model is a more general statement that gives guidance for treatment and suggests useful areas of research.
The biological model of addiction suggests that addiction is an inherited trait, similar to a genetic disease. It largely eliminates the idea that morality or societal influences are the main drivers of addiction. Rather, it suggests that addiction is inborn and when exposed to the opportunity, those vulnerable will take up the behavior. Other addiction models usually accept that there is some biological component, but don’t give it first place in the mix.
If the biological model of addiction is correct, it should show up in genetics. In general, this is true. If you track families, you find a larger proportion of addiction in the offspring of the addicted. Testing this biological model of addiction by looking at adoptions, where a son or daughter is raised by a non-addict family, also shows the pattern. The best test, that of twin studies (where the genome is almost identical) where the twins are raised in different circumstances, also shows the effect. Unfortunately, the correlation isn’t 100%.
Current estimates give a 25% allowance for genetic bias. That means that you can’t simply look at someone’s genetic heritage and tell if they will become an addict or not. They may be at a higher risk because of heredity, but it’s not guaranteed. For this reason, the biological model of addiction is often combined with a social model – meaning someone has to be exposed to addiction for the biology to play out. This “biosocial” model has more acceptance than biology alone.
The real difficulty comes because we haven’t been able to identify one or some combination of genes that we can say are causative. Family and hereditary evidence is one thing, but finding the actual gene seal s the deal. In fact, there is even controversy that family and twin studies show a clear effect. The answer probably lies with multiple pathways to addiction – some biological, some sociological and some the result of factors we haven’t identified yet.
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