Addiction and the Gut-Brain Axis

Key points

A poor gut microbiota can lead to a leaky gut and systemic inflammation.

Inflammation affects the brain, causing depression, anxiety, and poor impulse control.

This can lead to self-medication and multiple kinds of substance use disorders.

It doesn’t have to be this way. Source: Midjourney

Addiction carries a heavy mantle of social stigma . One-fifth of the population are afflicted, and it puts a burden on them, their friends, and their family members. It seems like a character flaw: Why can’t the addict simply quit?

But research is consolidating around a new view: Addiction has a connection to your gut microbes. This weird association is both intriguing and liberating. It’s intriguing that tiny gut microbes can run our lives into the ground, but it’s liberating because we can control our microbes with diet and lifestyle changes. At least 40 percent (and maybe more) of addicts may be helped or even cured by repairing a bad gut. How the Gut Alters Our Mood and Cognition

The story of the gut-brain axis is finally well accepted after two decades of brilliant, ground-breaking research. The gut, and the microbes therein, can alter our mood and cognition in three basic ways. From fastest to slowest, these include speedy nerve connections (via the vagus nerve ), slower immune system reactions, and leisurely hormonal secretions.

A healthy gut has microbes that produce butyrate, a chemical that nourishes and heals the cells lining the gut. Butyrate even reaches the brain where it can boost the production of new nerve cells, essential to learning and cognition.

Our planet is infused with invisible bacteria, fungi, and viruses. They coat every surface and float through the air. With everything we touch and every breath we take, we pick up microbes. To a bacterium, almost everything—including us—looks like lunch. For animals and plants to survive in this microbial miasma, we must conscript some of them to our side.

We typically think that our immune system fights disease-causing microbes, but that’s only half the story. Most germs are stopped dead in their tracks by our own microbes before our immune system is even aware of them. It takes a germ to fight a germ.

Our collection of microbes—our microbiota—coats our skin and our gut, providing complete round-the-clock protection. If it goes south, so does our health. When our gut microbes are imbalanced, our gut lining gets leaky, allowing microbes to sneak into our circulation. This unhealthy gut state is called dysbiosis.

Our heart obligingly pumps these germs and their toxins to every single organ in our body—including our brain. That is one way that our microbiota can affect our moods and cognition. With germs storming the gates, our brain becomes hypersensitive and finds it difficult to concentrate. We get anxious without quite knowing what the cause is. Self-Medicating a Troubled Mind

The poor communication between us and our guardian microbes is problematic. Depression has many legitimate causes, such as bereavement and loss, but it can also be the result of a quietly leaking gut. Not realizing that the cause lies in our gut, we may try to work around it by self-medicating.

Alcohol , nicotine, and drugs won’t help our gut, but in the short term, they may soothe a troubled mind. Unfortunately, these substances can exacerbate our gut issues. Alcohol can loosen the proteins that stitch the cells of our gut lining together, adding to gut leakiness. Unwittingly, we make a bad situation worse. It’s not a small issue: Half of the people with mood disorders are also addicted to something, and half of addicts have mood disorders.

A leaky gut leads to systemic inflammation, as our immune system tries to track down and kill rogue bacteria. This inflammation can affect the brain’s reward center, which drives cravings and pleasure-seeking activity. It also ramps up impulsive behavior. It’s an ideal setup for addiction. Worse yet, a dysbiotic gut can make withdrawal symptoms worse, discouraging abstinence.

In studies with rats, researchers found that 30 percent of them were hard-core consumers, even enduring electric shocks to get some alcohol. This special group had a distinctly different gut microbiota. Human studies have similar results: Some 40 percent of people with alcohol use disorders have significantly higher levels of depression and cravings than the rest, along with leaky guts and bad bacteria. These people also had higher rates of recidivism after detoxification.

While it is easy to understand how drinking can affect our gut, it is more of a leap to see how drugs that aren’t taken orally can do so. But a recent study found that both gut and oral microbiotas are profoundly different in cocaine users, with production of butyrate significantly reduced. Abstaining from cocaine helps to restore a healthy gut. Similar effects on the gut are observed with opioid use. The mechanism for this microbial disruption is murky, but the gut-brain axis goes both ways, and the brain may be the instigator of this dysbiotic cycle. Improving Gut Health for Recovery

Because we can control much of our gut microbiota with diet and supplements, we have a real opportunity to reduce the cravings and impulse control issues that lead to addiction. Vegetables, especially those high in fiber, are particularly effective for improving gut health. Fermented foods like sauerkraut and yogurt can also help. Probiotic and prebiotic fiber supplements are additional tools. Together, these could represent a solid first step toward recovery.

References

Gerace, Elisabetta, Simone Baldi, Maya Salimova, Leandro Di Gloria, Lavinia Curini, Virginia Cimino, Giulia Nannini, et al. “Oral and Fecal Microbiota Perturbance in Cocaine Users: Can rTMS-Induced Cocaine Abstinence Support Eubiosis Restoration?” iScience 26, no. 5 (April 20, 2023): 106627.

Meckel, Katherine R., Sierra S. Simpson, Arthur Godino, Emily G. Peck, Jonathon P. Sens, Michael Z. Leonard, Olivier George, Erin S. Calipari, Rebecca S. Hofford, and Drew D. Kiraly. “Microbial Short-Chain Fatty Acids Regulate Drug Seeking and Transcriptional Control in a Model of Cocaine Seeking.” Neuropsychopharmacology 49, no. 2 (January 2024): 386–95.

Leclercq, Sophie, Sébastien Matamoros, Patrice D. Cani, Audrey M. Neyrinck, François Jamar, Peter Stärkel, Karen Windey, et al. […]

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