An international team of economists, neuroscientists, and statisticians just released their third World Happiness Report, which measures well-being in countries around the world to help guide public policy.

Switzerland topped the list of the happiest nations, and all of the top eight countries were in the global north. Switzerland was followed by Iceland, Denmark, Norway, Canada, Finland, the Netherlands, and Sweden.

The United States ranked 15th, behind Mexico and Austria. Still, that's a slight improvement from the last report, in which the US ranked 17th.

The World Happiness Report isn't without a scientific basis.

One of its key findings, based on decades of neuroscientific and psychological research, suggests that keeping the brain happy relies on four main factors: 1) staying positive, 2) recovering from negative feelings, like a bout of sadness or anger, 3) caring about and spending time with family and friends, and 4) being mindful and allowing ourselves to feel "captured" by emotions like awe or joy.

Here are the 30 happiest countries from the study. Each color represents one of the six key factors (key below):

Happiness helps us live longer, healthier, and more productive lives, and cultivating that emotion early in life is key, according the 2015 report.

But not to worry: it's never too late to start.

Research shows that people who participate in meditation and mindfulness training programs (some as short as two weeks) tend to display changes in key areas of the brain connected to memory, perspective, and self-awareness. And a handful of recent studies have found a link between experiencing a sense of awe and feeling happier and more satisfied.

"These findings highlight the view that happiness and well-being are best regarded as skills that can be enhanced through training," the researchers write in their report.

With that in mind, here are the 10 least-happy countries, with Togo topping the list:

1. Togo

2. Burundi

3. Syria

4. Benin

5. Rwanda

6. Afghanistan

7. Burkina Faso

8. Ivory Coast

9. Guinea

10. Chad