The dopamine depletion model put forward by NIDA assumes that the drug is causing the addiction. That may sound obvious, but there are many other models of addiction which, while agreeing on the neuro-anatomy we have already outlined, interpret the findings differently. Some models of addiction would maintain that “addiction” actually precedes drug use. That probably sounds pretty counter-intuitive and so it will need a bit of explanation.
In 1988, two Italian researchers called Gaetano Di Chiara and Assunta Imperato proved that regardless of the class of drug, all drugs (whether sedatives, stimulants, opioids or even nicotine) achieve their effect by releasing dopamine at the Nucleus Accumbens.5 Multiple studies since seem to concur that all drugs and behaviors that are addictive, use the brains reward circuit (and therefore dopamine) to achieve their effects.
Then in 1990, Ken Blum and Ernest Noble, two American researchers, found that people who were low in dopamine receptor sites (presumably from birth) were more susceptible to alcoholism, drug addiction and numerous other compulsive behaviors.6
This led them to speculate that the ‘disease’ of addiction was actually more likely to be a genetic condition which preceded drug use. People who had less dopamine receptor sites felt more naturally unrewarded and were therefore more likely to get a medicinal effect from any drug they took and also more likely to repeat it.7 Blum termed this condition, Reward Deficiency Syndrome (RDS).
In the RDS model, people are seen to use drugs in order to self-medicate a natural lack of mid-brain dopamine function, which leaves them feeling miserable and un-pleasured unless they can find a source of dopamine strong enough to fix it (like drugs).
It’s worth noting ASAM’s original definition at this point;
“Addiction is a treatable, chronic medical disease involving complex interactions among brain circuits, genetics, the environment, and an individual’s life experiences.”
Whilst some people may be born ‘low-dopamine’ due to genetic variation, the same condition might also be created by environmental conditions, including excessive drug use.
Environments that are consistently unrewarding (especially in early childhood) may well have an effect on the development of dopamine receptors, and as we have already seen, repeated drug use can, in and of itself, destroy dopamine receptors sites. It all ends up with the same result. A person who feels catastrophically unrewarded, and who therefore needs to boost their mid-brain dopamine by any means necessary (drugs, food, sex etc.)