The Neurobiology of Addiction: Emotion, Impulse, and Decision-Making

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The science of addiction has come a long way in the past four decades. Everything from how we approach treatment to the way we talk about addiction has changed. Rather than labeling people with alcohol and drug use problems as drunks, alcoholics, addicts, or junkies, we now use terms that minimize stigma and promote an evidence-based understanding of the complex phenomenon of addiction. Instead of drunk or alcoholic, we say a person with an alcohol use disorder. Instead of addict or junkie, we say a person with a substance use disorder.

The changes in treatment mirror the changes in the way we talk about the disordered use of alcohol and substances. Rather than isolating people and expecting them to quit cold turkey when they seek treatment and support, high-quality treatment centers now create individualized treatment plans that address the entire person. This integrated, holistic approach to treatment often includes medication-assisted detox to help prevent relapse for those new in recovery, a step-wise approach to recovery that leverages strengths and addresses weaknesses, and an awareness of all the biological, social, and psychological factors that contribute to the disordered use of alcohol and substances.

All these changes stem from a shift away from the moral failure/lack of willpower model of addiction to the disease model of addiction. Whereas the former model held that addiction was the result of a character flaw or poor decision-making, the latter model proposes that addiction is a chronic, relapsing medical condition that responds well to integrated treatment, the same way other chronic, relapsing medical conditions such as diabetes or hypertension.

Recent research from scientists at the University of Southern California sheds light on how addiction impacts specific areas of the brain – and how those areas of the brain may contribute to long-term misuse of alcohol and substances.

Addiction and the Brain

In the paper “A Neurobehavioral Approach to Addiction: Implications for the Opioid Epidemic and the Psychology of Addiction” a group of researchers connect the dots on how changes in a trio of brain regions – the frontal and prefrontal cortex, the amygdala, and the insula – combine to affect the way people develop and maintain the disordered use of alcohol and substances.

To understand how those brain regions affect addiction, let’s first take a look at what they do:

Frontal/Prefrontal Cortex

The frontal cortex of the brain integrates incoming sensory stimuli and regulates the planning of appropriate responses to those stimuli. The prefrontal cortex takes the integration performed by the frontal cortex a step further. It aids in attention, predicting the consequences of behavior, controlling impulses, managing reactions to emotion, making future plans, and coordinating and regulating complex behaviors, such as “If action A leads to action B, and I want the outcome of action B, I need to take action A.” Together, the frontal and prefrontal cortex areas are known as the executive function areas of the brain, since they offer the final input on decisions related to actions and behavior.

The Amygdala

The amygdala is part of the limbic – a.k.a. reward – system of the brain. That means it’s involved in pleasure, motivation, emotional regulation, and behavior. The amygdala is an integrative brain region: it receives signals from areas that generate emotion and sends signals to areas that result in behavior.

The Insula

Also known as the insular cortex, the insula plays a key role in sensations directly related to survival needs. It sends signals to the amygdala and the frontal/prefrontal cortex about the state of the internal organs and reports homeostatic imbalances, such as pain, stress, reward, and uncomfortable physical states associated with withdrawal from substances of misuse.

Scientists have known for years about the contributions of the amygdala and the frontal/prefrontal cortex to addiction. In summary, long-term exposure to substances of misuse increases the influence of the reward system – regulated by the amygdala – over the frontal/prefrontal cortex. Long-term exposure to substances of misuse also degrades the performance of the frontal/prefrontal cortex – the executive decision-making area of the brain – which negatively affects rational decision making and overall cognitive function.

New Data: The Role of the Insula

What scientists learned in this latest study is that the insula can affect both the amygdala and the frontal/prefrontal cortex – and that the action of the insula on the amygdala and frontal/prefrontal cortex may have a greater impact on addiction than previously thought.

To understand this impact further, we need to dive deeper into what the insula does, and take a look at previous research on the effect of stroke-related brain damage on nicotine addiction.

First, to the stroke-nicotine connection: in 2007, a group of neuroscientists discovered that heavy smokers who experienced a mid-cerebral-artery stroke that caused damage to the insula subsequently quit smoking “immediately and effortlessly.” Anyone who knows anything about quitting an addiction knows the process is rarely immediate and almost never effortless. That’s why this finding intrigued researchers, who then determined that any stroke-related lesion (damage) to the insula increased the odds of quitting smoking at least five-fold.

To explain this phenomenon, the research team looked to recent studies showing detail on the function of the insula. Here’s what those studies reveal about the insula:

“The insula…communicat[es] interoceptive cues to the brain, which play a role in the subjective experience of emotional states. Interoceptive cues may be the basis for the experience of craving and the urge to use a drug. Interviews with people who have an addiction reveal that they often feel the need to use in order to feel normal. This could be related to interoceptive cues signaling a homeostatic imbalance.”

Let’s get on the same page. Interoceptive means “relating to stimuli produced within an organism, especially the gut and internal organs.” Therefore, the insula plays a role in communicating signals from our internal organs – our heart, lung, and digestive system – to our brain. The USC research team then made their most important connection.

Addiction and Homeostatic Imbalance

Each drug of misuse causes a wide range of physiological reactions, from the euphoria and pleasure people experience when they take the drug to the discomfort, pain, and anxiety they experience in the absence of the drug. These physiological reactions manifest all over the body: in heart rate, breathing rate, the immediate sensations related to substance use – i.e. the feeling of smoking or the sensation of drinking – and in the feelings of pleasure and reward generated by our brain.

In other words, drug use affects homeostasis, or the balance of our internal systems. When we take a drug for a long time, our body achieves a new homeostasis that’s partially mediated by the presence of the substance of misuse. If we stop taking that drug, the substance-influenced homeostasis become imbalanced. When that happens, the insula reports this imbalance up the neurological chain of command, first through the amygdala, and then through the frontal/prefrontal cortex. In fact, researchers found that the insula sends information to the amygdala and cortex simultaneously.

And here’s the big news: signals from the insula can amplify reward messages from the amygdala and attenuate the action of the prefrontal cortex. That means that in some cases, the insula compounds cravings and impairs our ability to process craving rationally. Or, in the words of the study authors:

“Activity in the insular cortex elicited by homeostatic imbalance, such as deprivation states, withdrawal, pain, stress, or reward cues, serves to sensitize the motivational circuits that propel individuals toward reward and to hijack the prefrontal cortical system, preventing it from using the cognitive resources necessary to resist reward.”

What This Means for People in Recovery

This is an important step forward in our understanding of how the brain functions in people with alcohol and/or substance use disorder. This new knowledge not only supports the disease model of addiction, but can also help people in recovery understand why they have such a hard time resisting cravings.

Here’s how.

The last part of the quote above indicates that the action of the insula prevents the prefrontal cortex from using the tools it needs to resist reward. This means that the power of cravings – and the inability to resist them – has a neurological basis. The insula increases the desirability of a drug (amplifies amygdala), decreases the ability to make a rational decision about using the drug (impairs prefrontal cortex), which makes the decision to use the drug easy: all the internal signals say yes.

When someone in recovery knows this, they can use the coping skills they learn in treatment to ride out the intense urges and cravings – because they know cravings are cyclical and will eventually pass. They can use the support of counselors and recovery peers to get them through the difficulties and make it through to the other side – without relapsing. And in some cases – especially early in recovery – they may use medication to help manage the cravings.

Restoring Balance

Finally, when a person in recovery learns and builds the skills to manage cravings and avoid relapse, they move – one day at a time – to a new homeostasis. They rebuild their internal processes and create a robust and resilient brain and body. They achieve a balance that promotes sobriety and increases their chance of sustained, long-term recovery. This new knowledge from the field of neurobiology helps them understand that though their addiction may have caused imbalances in their brain and body, those imbalances can heal. They can learn to manage their cravings, restore their sense of agency, bolster their self-esteem, and empower themselves to live life on their own terms.