What Really Happens to the Brain in Addiction?

Last updated on November 4th, 2019

Every day, in my clinical practice, I explain the neurobiology of addiction to patients and their families, and they find it helpful. Although there is much to be learned, we know quite a bit about how this works. But how it works is quite different from what is commonly communicated by many organizations, including federal agencies, or what is taught in rehabs. In fact, much of what is propagated is either oversimplification or downright false. (For this article, I’m using the term addiction referring only to substance use disorders (SUD), not “process addictions” like compulsive gambling or sexual activity.)

First, the real game-changer: a substance use disorder (SUD) is a result of exposure to an intoxicant. Addiction results from prolonged exposure to high levels of a particular drug (including alcohol or nicotine,) to a genetically vulnerable brain. The brain then adapts, in an attempt to restore “normality.” This process of neuroadapatation results in the symptoms of addiction.

The three cardinal symptoms of addiction are: 1) impaired control over use once it starts, 2) preoccupation and craving, and 3) an almost delusional rationalization that “this time will be different,” even though the last 99 percent of use episodes resulted in disaster.

In this way, addiction is end-organ (brain) damage that results from heavy substance use, much the same way that stroke and heart failure are end-organ damages resulting from excessively high blood pressure. The degree of neuroadapation ranges from mild to severe. Thus, some people have very mildly, and potentially irreversible, SUD, others have a more advanced disorder that might require treatment, while others have severe, recurrent, treatment-refractory addiction where we are unable to arrest the progression. However, there is no reason to believe that the process is any different for mild versus severe SUD, other than degree.

However, we aren’t born with addiction, but with a genetic vulnerability to it. Addiction, like most behavioral/mental health disorders, is about 50 percent genetic and 50 percent environmental. Most of the genetic vulnerability for addiction and most mental disorders is not specific to a specific disorder, but is shared among anxiety, mood disorders, attention deficit disorder, personality disorders and possibly others. That is, there are likely hundreds or even thousands of genes underlying these disorders, each contributing a tiny amount of the vulnerability.

Addiction, like most behavioral/mental health disorders, is about 50 percent genetic and 50 percent environmental.-Mark Willenbring

The most prominent trait associated with addiction is behavioral under-control or disinhibition, which refers to a relative lack of ability to inhibit socially undesirable behavior – or, perhaps, simply “liking getting high.” (Hint: not everyone likes getting high!) Another is neuroticism, which is the tendency to experience excessive or inappropriate negative affects such as anxiety and depression. In addition to these shared genetic traits, there are genetic traits that are specific to a specific substance. Examples of specific genetically influence traits include feeling stimulated rather than sedated by a central nervous system depressant such as alcohol or opioids. Another is relative insensitivity to intoxication, which allows some people to drink or use more than other people without adverse effects.

Often, environmental events are required for the underlying genetic vulnerability to be expressed. Obviously, access to the intoxicant is required. If no use occurs, there can be no SUD. Although this may seem obvious, some prominent experts assert that “we are born with addiction,” that a SUD is present at birth even without exposure. This assertion is both wrong and absurd, as well as not consistent with current neurobiological understanding of SUDs.

Perhaps the strongest environmental trigger, in addition to access, is early childhood neglect and abuse.-Mark Willenbring

Perhaps the strongest environmental trigger, in addition to access, is early childhood neglect and abuse. Early childhood neglect in particular appears to result in changes in gene expression through a process called epigenetics. (I’ll write more about epigenetics in a later piece.) That is, some of the genes that affect risk of SUD development are not expressed unless triggered by the environmental effects. This is why social policies are important factors in contributing to risk of SUD development. Lack of access to health care, housing, and nutritious food, coupled with unemployment, low income and chronic stress, trigger this adverse genomic expression, thus resulting in higher rates of mental and addictive disorders than would be the case otherwise.

Finally, the neuroadaptations in the brain that result from the combination of genetic vulnerability and environmental triggers are substance-specific. That is, the dysregulation of consumption (of the intoxicant) only applies to the specific drug consumed. It does not apply to other drugs. It has been conclusively demonstrated that “cross-addiction,” where a person stops using one drug but becomes addicted to another one, seldom occurs, if at all. For example, in my practice, I find that opioid addicts seldom like alcohol, and vice versa.

A final note. The information presented in this blog contradicts some commonly held beliefs among treatment providers and recovering people. This may cause discomfort, but I believe it is important to change what we think or believe when the facts change. And they have.
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