Scientists may have found a brain chemical that helps us break bad habits

If you’ve ever wondered why some habits seem so hard to shake, new research suggests the answer may have less to do with willpower than we think. Scientists say a key brain chemical could play an important role in helping us let go of old behaviours and embrace new ones.

Whether you’ve promised yourself you’ll stop scrolling before bed, stop sneaking that extra biscuit or finally stop biting your nails, you probably know how frustrating it can be when good intentions aren’t enough.

We tend to think of habit change as a question of willpower. We admire people who seem disciplined, blame ourselves when we slip up. Most importantly, we assume that if we really wanted to change, we’d simply do it.

But what if breaking a habit isn’t just about determination?

According to new research from Japan, our ability to let go of familiar behaviours and embrace new ones may depend partly on a little-known brain chemical called acetylcholine.

The findings offer a fascinating glimpse into how the brain decides when it’s time to stop repeating the past and try something different.

The study, published in Nature Communications, explores what scientists call “behavioural flexibility” – the brain’s ability to adapt when familiar strategies stop working. Researchers say this process may help explain why some people find it particularly difficult to break entrenched patterns, including those linked to addiction, obsessive compulsive disorder (OCD) and Parkinson’s disease.

What happens when a habit stops working?

To understand this, researchers turned to a surprisingly relatable scenario: what happens when something that has always worked suddenly stops?

The team trained mice to follow a route that led to a reward. Over time, the animals learned the pattern and stuck with it. Then the researchers changed the rules and moved the reward elsewhere.

Faced with an unexpected setback, the mice had a choice: stick with the familiar or search for a new solution.

That’s where acetylcholine appeared to come into play.

The researchers found that when the expected reward failed to appear, levels of acetylcholine increased. The greater the increase, the more likely the mice were to abandon their old behaviour and try something new.

“Neurally, we saw a significant increase in acetylcholine release in certain areas of the brain. And behaviourally, we saw more mice displaying what’s known as ‘lose-shift’ behaviour, changing their choices in the maze after non-reward,” says Dr Gideon Sarpong, first author of the study.

“The greater the increase in acetylcholine the more likely the mice were to change their future choices. Our results demonstrated the importance of acetylcholine in breaking habits and enabling new choices to be made.”

When researchers reduced the animals’ ability to produce acetylcholine, that flexibility largely disappeared. The mice became less willing to change course, even when their old strategy was no longer delivering results.

Could this help explain addiction and OCD?

Behavioural flexibility involves many different brain systems. However, researchers believe acetylcholine plays an important role in helping us adapt when familiar routines stop serving us.

“It’s an important piece of the puzzle, as the activity of the striatum, where these cholinergic interneurons are held, is a central component of this system,” says Professor Jeffery Wickens.

The findings may eventually help researchers better understand why some people become trapped in repetitive thoughts and behaviours.

“In particular, with conditions such as addiction and obsessive-compulsive disorder we see a difficulty in breaking habits and shifting behaviour. So, understanding the mechanics of behavioural flexibility may one day help us develop better treatments,” says Professor Wickens.

The study doesn’t suggest that willpower is irrelevant. But it does challenge the idea that changing behaviour is simply a matter of trying harder.

For anyone who has ever wondered why a habit can feel so stubbornly resistant to change, that’s a meaningful insight. Sometimes the challenge isn’t a lack of determination. It’s that the brain is built to prefer what is familiar. But it’s also built, in its own way, to recognise when it’s time to try something new.

Words: Lucy Rawlinson, Images: Shutterstock