Microglia – Your Brain’s Immune Cells and What Alcohol Does to Them

Microglia are the brain’s own immune cells. They patrol nerve tissue, clear away cellular debris, and are the first to respond when something in the brain goes wrong. Research on microglia and alcohol shows that heavy drinking can push these cells into a lasting state of alarm. That may help explain why mood, sleep, and cravings can keep giving you trouble long after your last drink.

What Microglia Do in a Healthy Brain #

Microglia belong to the glial cells, the support crew that nourishes and protects your neurons. Unlike other brain cells, they originally come from the immune system. They migrate into the brain very early in development and stay there for life.

At rest, microglia extend fine branches into their surroundings and constantly scan them. They remove dead cells and protein waste. They also help remodel the connections between nerve cells by pruning synapses that are no longer needed and making room for new ones. That makes them part of neuroplasticity, the brain’s ability to rewire itself.

When microglia detect a threat, they change shape and behavior. They release immune signaling molecules called cytokines. In the short term, that is useful. But if the alarm never switches off, it can damage nerve cells. Researchers call this state neuroinflammation, a silent inflammation in the brain.

How Alcohol Puts Microglia on High Alert #

Based on current research, alcohol reaches microglia by two routes. The first runs directly through the brain. Alcohol triggers the release of danger signals there, such as a protein called HMGB1. This protein binds to specific sensors on microglia known as toll-like receptors. The cells then switch into defense mode.

The second route runs through your gut. Heavy drinking makes the intestinal wall more permeable, a condition often called leaky gut. Fragments of gut bacteria then slip into the bloodstream, especially lipopolysaccharides (LPS). These bacterial toxins ramp up inflammation throughout the body, and the signal reaches the brain as well. In one mouse study, animals that had been given alcohol beforehand showed a much stronger inflammatory response in the brain to these toxins than animals without alcohol. You can read more about this connection in our entry on the gut-brain axis.

One important caveat: these mechanisms have mostly been described in animal studies and cell cultures. Together they form a convincing model, but only parts of it have been confirmed in humans so far.

Priming: Why Every Binge Leaves a Mark #

One especially interesting effect is what researchers call priming. Microglia that have been strongly activated once do calm down again. But they stay more sensitive. The next time they are triggered, they react faster and harder.

In animal models, this oversensitivity builds with every drinking episode and every withdrawal. That closely resembles the kindling effect, in which repeated withdrawals make the brain increasingly irritable. Whether the two are directly linked in humans has not been established yet. Still, the parallel is striking. It also fits the observation that repeated binge drinking is particularly hard on the brain.

Microglia and Alcohol in Humans: What Has Actually Been Measured #

In humans, the findings are less clear-cut than in animal studies. Postmortem studies of people with alcohol use disorder found more microglial markers and more inflammatory signaling molecules in several brain regions than in comparison brains. That points to activation.

Brain imaging in living people, however, produced a surprising result. A specialized PET scan can make visible a protein that activated microglia produce in larger amounts. Two studies published in 2017 found not more but less of this marker in people with alcohol use disorder. In the British study, the difference showed up mainly in the hippocampus, the brain’s memory hub. The participants there had been sober for only a few weeks.

How does that fit together? One possible explanation is that activated does not automatically mean inflamed. Microglia can take on several different states, including one that is more focused on repair. In rat studies, alcohol sometimes produced exactly this state. It is also possible that years of drinking wear microglia out or reduce their numbers. On top of that, the PET marker is not found in microglia alone. The honest summary: alcohol changes microglia in humans too, but the full picture is still incomplete.

Microglia, Mood, and Cravings #

The signaling molecules released by activated microglia do more than drive inflammation. They also affect communication between nerve cells, the reward system, and how your brain handles stress. Researchers therefore suspect that they play a role in every stage of the addiction cycle. That includes the high, the low mood during withdrawal, and the later urge to drink again. In people with alcohol use disorder, certain immune markers in the blood have been linked to the intensity of cravings.

This could help explain why many people still feel flat, joyless, or foggy for weeks or months after they quit. Anhedonia, brain fog, and sleep problems are all part of PAWS, the extended phase after acute withdrawal. An overactive immune response in the brain is a plausible contributor. In humans, though, that link has not been proven yet.

Do Microglia Recover in Sobriety? #

There is good news here, although once again it comes mostly from animal research. Once alcohol is out of the picture, microglia gradually return to their resting state. In one rat study, activated microglia even helped the brain recover afterward. So they are not only the arsonists. They are also part of the repair crew.

What happens in the rest of your body matters for this recovery. As the gut lining heals, fewer bacterial toxins enter the bloodstream. Good sleep supports the glymphatic system, your brain’s nightly cleaning cycle. And less chronic stress lowers the overall readiness for inflammation. All of this takes time. That is why it makes sense to see the first months of sobriety as a healing phase, not just a waiting period.

Are There Medications That Calm Microglia? #

Because microglia seem to play such a central role, researchers are looking for drugs that can calm them down. The furthest along is ibudilast. It has been approved in Japan for other conditions for decades and dampens the activity of glial cells, among other effects. In a small US study of 52 people with alcohol use disorder, two weeks of ibudilast measurably lowered the odds of heavy drinking days. At the same time, the brain’s reward center reacted less strongly to alcohol cues in brain scans. The drug had no measurable effect on mood, however.

Ibudilast is not FDA-approved, either for alcohol use disorder or for any other use, and larger trials are still needed. Lab data also suggest that various natural compounds can dampen microglia. Solid studies in people with alcohol use disorder are still missing, though.

What This Means for Your Recovery #

Microglia research allows a few conclusions, even if much of it is still preliminary. Every binge and every withdrawal may further sensitize your brain’s immune defenses. That is one more argument for stable sobriety instead of an ongoing back-and-forth. It is also another reason why quitting cold turkey without medical supervision is not a good idea.

At the same time, the research shows that your brain is not a helpless victim. Its immune cells can settle down and even help with repairs. If you don’t feel as good as you hoped in your first months of sobriety, that is not a sign of failure. It may simply mean that your brain is still cleaning up.

Connect with others who’ve been there in our Bye Bye Booze community. Many members know this tough stretch from their own experience.

FAQ About Microglia And Alcohol #

References #

• Coleman LG Jr, Crews FT (2018): “Innate Immune Signaling and Alcohol Use Disorders.” Handbook of Experimental Pharmacology, 248:369–396.
• Qin L et al. (2008): “Increased systemic and brain cytokine production and neuroinflammation by endotoxin following ethanol treatment.” Journal of Neuroinflammation, 5:10.
• He J, Crews FT (2008): “Increased MCP-1 and microglia in various regions of the human alcoholic brain.” Experimental Neurology, 210(2):349–358.
• Hillmer AT et al. (2017): “In vivo imaging of translocator protein, a marker of activated microglia, in alcohol dependence.” Molecular Psychiatry, 22(12):1759–1766.
• Kalk NJ et al. (2017): “Decreased hippocampal translocator protein (18 kDa) expression in alcohol dependence: a [11C]PBR28 PET study.” Translational Psychiatry, 7(1):e996.
• Marshall SA et al. (2013): “Microglial activation is not equivalent to neuroinflammation in alcohol-induced neurodegeneration: the importance of microglia phenotype.” Neurobiology of Disease, 54:239–251.
• Zhao YN et al. (2013): “Activated microglia are implicated in cognitive deficits, neuronal death, and successful recovery following intermittent ethanol exposure.” Behavioural Brain Research, 236:270–282.
• Grodin EN et al. (2021): “Ibudilast, a neuroimmune modulator, reduces heavy drinking and alcohol cue-elicited neural activation: a randomized trial.” Translational Psychiatry, 11:355.

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