PET Scans Reveal Brain Changes in Addicts

The stigma surrounding addiction is hard to avoid. While you may picture someone who is addicted to drugs as having some type of moral failing or a personality issue, doing the same thing for other diseases would be unthinkable. This is why experts are pushing for the proper recognition of drug and alcohol addiction (as well as behavioral addictions) as diseases. There are many reasons to support this conclusion, but some of the most convincing is PET scan evidence showing the brain changes common in addiction.

Defining Addiction — How Our Understanding Is Growing

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders classifies addiction as a “substance use disorder,” and although different substances are classified as different disorders, they all share the same broad criteria. From the previous incarnation of the DSM, there have been a few changes, most notably the removal of “problems with law enforcement” as a criterion (because cultural differences made the criteria inapplicable in some countries), which has been replaced with another criterion related to cravings.

Thinking about another condition — such as diabetes — shows why the removal of “problems with law enforcement” as a criterion helps to establish the disease nature of addiction. If the criteria for diabetes included “social problems at parties with sugary treats,” whoever wrote it would be rightfully chastised for suggesting that a disease can be defined by its socially and culturally-dependent consequences. For drug addiction, this same type of thing (the legal problems are ultimately imposed by society, not caused by the condition itself) previously passed though the various edits, reconsiderations and proofreads unscathed. Removing this is just the start, but at least it’s a step in the right direction; the replacement, cravings, is a genuine symptom of the disease of addiction.

Substance Abuse vs. Addiction

As difficult as it may be for some people to see the distinction, it’s possible to abuse substances without being addicted. The woman who drains a bottle of wine on a Saturday night is definitely abusing substances in that she is clearly going beyond the recommended limit (into binge drinking) to increase the drug’s effects. But if she doesn’t drink again for a month, addiction is obviously not a factor. It’s possible for people to “occasionally” abuse substances without becoming addicted, such as by drinking too much in social situations and then returning to non-use. But when addiction takes hold, it’s not something you can just step out of. The structural and functional changes to the brain are full time and take prolonged periods of abstinence to correct.

PET Scans and the Neurobiology of Addiction

Addiction is a brain disease. It’s a chronic problem, progressing over time from impulsive behavior coupled with positive reinforcement (the short-lived, seemingly-beneficial effects of a substance) to a compulsion held in place by negative reinforcement (the encouragement to continue in order to prevent unpleasant withdrawal symptoms). This all comes down to neurobiology and especially the phenomenon of plasticity, where the brain physically changes in response to external stimuli.

Using positron emission tomography (PET scans) and other techniques, researchers over the past two decades have drastically improved our understanding of the neurobiology of addiction. The core point is that addiction impacts the brain circuits that control reward, motivation, memory and inhibitions.

The chemical at the center of most addictions in dopamine, the “pleasure” chemical you get from other activities such as eating and having sex that is designed to both reward you for engaging in such activities and motivate you to do so again. A dopamine-releasing experience is coded into your memory as if your brain says, “This is an experience to seek out — remember exactly what caused it and try to find it again.” Naturally, this motivates us to engage in important experiences, but when an external substance is the cause, it can motivate us to seek out our drug of choice instead.

The real problems start when the brain is accustomed to having the dopamine boost flood the core reward area, the nucleus accumbens, and the effect of the drug starts to diminish. The brain structure has changed to accommodate this unnatural flood of feel-good chemicals, and taking the same dose no longer has the same effect. The brain literally becomes dependent on the external chemical, so if you don’t take it, you end up with a chemical imbalance and withdrawal symptoms. Compulsion and cravings are free to take over at this point; the drug has effectively hijacked the brain and made itself the ultimate prized commodity at the expense of all else.

Just like type 2 diabetes is made more likely by dietary choices that lead to a deficiency of insulin and therefore the development of the condition, drug addiction is made more likely by regular use of a substance, which leads to the changes in neurochemistry and brain function that characterize the issue. With PET scan evidence showing the physical changes in the brain, there is little doubt that addiction is a disease like any other. The more we can accept and understand this, the less we’ll unfairly stigmatize those suffering from it.

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