Ever had someone tell you to cheer up and smile? It’s probably not the most welcomed advice, especially when you’re feeling sick, tired or just plain down in the dumps. But there’s actually good reason to turn that frown upside down, corny as it sounds. Science has shown that the mere act of smiling can lift your mood, lower stress, boost your immune system and possibly even prolong your life.

It’s a pretty backwards idea, isn’t it? Happiness is what makes us smile; how can the reverse also be true? The fact is, as Dr. Isha Gupta a neurologist from IGEA Brain and Spine explains, a smile spurs a chemical reaction in the brain, releasing certain hormones including dopamine and serotonin. “Dopamine increases our feelings of happiness. Serotonin release is associated with reduced stress. Low levels of serotonin are associated with depression and aggression,” says Dr. Gupta. “Low levels of dopamine are also associated with depression.”

Fake It Till You Make It

In other words, smiling can trick your brain into believing you’re happy which can then spur actual feelings of happiness. But it doesn’t end there. Dr. Murray Grossan, an ENT-otolaryngologist in Los Angeles points to the science of psychoneuroimmunology (the study of how the brain is connected to the immune system), asserting that it has been shown “over and over again” that depression weakens your immune system, while happiness on the other hand has been shown to boost our body’s resistance.

“What’s crazy is that just the physical act of smiling can make a difference in building your immunity,” says Dr. Grossan. “When you smile, the brain sees the muscle [activity] and assumes that humor is happening.”

In a sense, the brain is a sucker for a grin. It doesn’t bother to sort out whether you’re smiling because you’re genuinely joyous, or because you’re just pretending.

“Even forcing a fake smile can legitimately reduce stress and lower your heart rate,” adds Dr. Sivan Finkel, a cosmetic dentist at NYC’s The Dental Parlour. “A study performed by a group at the University of Cardiff in Wales found that people who could not frown due to botox injections were happier on average than those who could frown.”

And there are plenty more studies out there to make you smile (or at least, serve as reference for why you should). Researchers at the University of Kansas published findings that smiling helps reduce the body’s response to stress and lower heart rate in tense situations; another study linked smiling to lower blood pressure, while yet another suggests that smiling leads to longevity.

Smiling Helps On A Day-To-Day Basis

Studies aside, there are plenty of living, breathing, smiling humans who can testify to the fact that looking the part of happy helps them get through the day.

“Smiling absolutely changes the way I think and feel,” says Jaime Pfeffer, a success coach and meditation instructor based in Florida. “My husband and I purposely spend 60 seconds every morning smiling to supercharge our mood. It's part of our morning routine. If something goes awry during the day, I usually use smiling to quickly shift my mood. It only take 10 to 15 seconds for it to make a difference for me now. It helps me to feel less stressed, transform my mood quickly and put things in a different perspective.”

Pfeffer adds that she recommends smiling to all her clients, particularly when they’re dealing with long days or tedious work. “One of my clients last week told me smiling for 30 seconds at a time a few times per day helps him stay upbeat when doing sales calls. He said the task can get old after a while, but the smiling helps him stay more energized and avoid burnout.”

Travel writer Clemens Sehi uses a smile not just to feel better, but also as a way of setting an amicable tone with strangers abroad.

“When traveling there is one thing that one realizes quite fast: a smile can change everything. It can open doors and the hearts of other people whose culture you do not even know. A smile is the most international language that everyone knows.”

How Smiling Goes Viral

A smile is also something that is easy to pass on. Much like yawning, smiling is contagious.

“This is because we have mirror neurons that fire when we see action,” says Dr. Eva Ritzo, a psychiatrist and the co-author of "The Beauty Prescription: The Complete Formula for Looking and Feeling Beautiful." As its name suggests, mirror neurons enable us to copy or reflect the behavior we observe in others and have been linked to the capacity for empathy.

On a less mechanical level, there’s also the idea that when we see a smile, we want to reciprocate because we feel endeared.

“Smiling is contagious not just because of how a smile looks from the outside, but also because of the intention and the feeling that is put behind a smile,” says Jasmine Wang, communications manager at Smile Train, a charity providing corrective surgery for children with cleft lips and palates. “When someone smiles at you, you feel the good vibes from them, which makes you want to pass a smile on the next person, and so on and so forth. We should make a conscious effort not to take smiles from our loved ones for granted, and to keep in mind that across the globe a smile can mean so much more than a simple facial movement.”

A smile’s contagion is so potent, that we may even be able to catch one from ourselves. Dr. Ritzo recommends smiling at yourself in the mirror, an act she says not only triggers our mirror neurons, but can also help us calm down and re-center if we’re feeling low or anxious.

It turns out there's solid evidence that smiling can do us a world of good. Since researching this piece I’ve been conducting my own little smile experiments. I tried smiling when I tensed up in traffic yesterday, and again during a rigorous workout and then today when I woke up with a headache. I found that it feels completely incongruous to smile when I’m tense or tired, and there’s a strange sense of departing a comfort zone. But I have to admit, instantly I was calmer, less upset and, maybe just ever so slightly for a second, smiling made me feel happy.