The famous 90-year-old Buddhist monk and author Thich Nhat Hanh once said: “Sometimes your joy is the source of your smile, but sometimes your smile can be the source of your joy.”

He’s right. The biochemical processes set in motion when you smile do actually make you feel better. We know this thanks to a long history of scientific interest in facial expressions going way back before Thich Nhat Hanh’s time to Charles Darwin.

The expression of emotions on the face are one of the most socially significant human behaviours, and much of the interest has been looking at the role of emotional expressions as social signals of internal states, and how we recognise their expressions in others.

But there has also been a line of inquiry into the possibility that facial expressions aren’t just representations of internal states, but can themselves affect emotional experiences. This idea has become known as the Facial Feedback Hypothesis (FFH).

Over the years it’s been consistently proved that a smile increases the intensity of emotional experience. Scientists therefore thought that inhibiting facial expressions might lower the intensity of emotional experience, but this hasn’t been the case.

Studies suggest that facial feedback influences rather than completely determines emotional experience, so a weaker version of FFH has been seen as the more realistic.

If all of this sounds a bit confusing, here is what matters most to you:

  • Smiling makes you feel better
  • You’re more likely to smile if you feel comfortable about your teeth
  • So looking after your teeth isn’t just good for your oral health, it’s good for your emotional wellbeing

Another thing the research tells us is that having anti-wrinkle injections won’t affect the intensity of your emotional experiences. Several studies into FFH have featured anti-wrinkle injections.

In one, ten patients with ongoing treatment-resistant major depression were given anti-wrinkle injections and two months later nine of them were no longer clinically depressed, suggesting that anti-wrinkle injections — and facial feedback — may affect mood.

So, why do we feel better when we smile? Intentionally exercising your zygomaticus major muscle and orbicularis oculi muscle — which you can do by holding a pencil with your teeth — fires a signal to the brain, stimulating your reward system to release endorphins, your happy hormones.

You’ve just jump-started the positive feedback loop of happiness. When your brain feels happy, you smile; when you smile, your brain feels happier.

So if you want to feel good, you know what to do. Smiling reduces anxiety and lowers your blood pressure and heart rate, delivering a happiness level that’s been estimated as equivalent to that of having 2,000 bars of chocolate, or winning €18,000. How’s that for something to make you smile?