Alcohol is bad news for the body. Overload your liver with alcohol once in a while, and you’re almost guaranteed a headache paired with dehydration and feeling like shit the next day. But if alcohol becomes a habit, you can start developing a tolerance. The human brain gets used to sitting in a soup of alcohol and starts to resist attempts to give it up.

So what happens to the brain when someone quits drinking altogether? Here’s a play-by-play.

The Brain’s “Reward” System Makes It Hard to Stay Quit

First, things get a little crazy. Scientists have studied the brains of people who struggled with alcoholism after they died. Those brains have fewer receptors for dopamine — a “reward” chemical that’s not fully understood, but researchers know plays an important role in pleasure and influence in decision making.

Alcohol stimulates the brain to release dopamine. Cut it out of a user’s life, and their dopamine levels drop sharply. That, along with the reduced number of receptors, likely plays a role in feelings of sadness and lack of motivation that can follow quitting alcohol.

But a follow-up experiment on rats shows a secondary effect that can happen days or weeks after quitting: Even with lower dopamine production, the reduced count of receptors in the brain means less dopamine is getting used up, so it slowly builds up — until there’s way more dopamine hanging around than in a healthy brain.

All this screwiness with reward and decision systems likely plays a role in why it can be so hard for people with alcoholism to kick the habit and have it stay kicked.

Brain Tissue Stops Deteriorating and Can Even Become Healthier

Dopamine isn’t the only thing that changes, though. Alcohol also screws with a chemical known as thiamine, which is necessary for keeping brain tissue functional and healthy. Long periods of intense alcohol use can damage brain tissue, leading to short- and long-term problems with coordination, thinking, and perception. Stop drinking, and that thiamine builds up again (especially with the aid of supplements), which can reverse some of the damage. Other, broader nerve damage in the brain might never reverse itself — but it won’t keep getting worse.

It Gets Easier to Maintain Healthy Habits

Even people who don’t drink enough to cause significant tissue damage to their brains experience some serious brain-related health impacts from alcohol.

Sleeping and eating especially suffer. Booze might help people fall asleep if they drink just before going to bed, but it reduces the quality of that sleep. So the value of seven hours of drunken sleep is much lower than seven hours of sober sleep. And that long-term sleep deprivation has severe health impacts that may start to clear up when users quit.

Similarly, drinking makes it harder to eat healthy, with research showing that even moderate drinkers eat far worse on drinking days — with real effects on obesity. Quitting alcohol makes it easier for users to cut unhealthy foods out of their lives, and get healthier all around.

Photos via Getty Images / Daniel Berehulak