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Molly Cranna for TIME

It’s Official: Happiness Really Can Improve Health

Scientists have thought for years that happiness may have a real effect on physical health, but a comprehensive new review makes the case stronger than ever.

The review, published in Applied Psychology: Health and Well-Being, examines the effects of “subjective well-being”—a measure of how people evaluate their own lives—on various aspects of physical health. The topic has been studied extensively; the paper references more than 20 previous literature reviews and more than 150 individual studies.

These studies have confirmed, with “almost no doubt,” that happiness really can influence health, says lead author Edward Diener, professor of social psychology at the University of Utah. They’ve also put forth several theories of how this might happen. For one, happy people likely take better care of themselves and choose healthy behaviors—like exercising, eating well and getting adequate sleep—over unhealthy ones.

There’s also evidence that happiness can have beneficial effects on the cardiovascular and immune systems, influence hormones and inflammation levels and speed wound healing. It’s even been linked to longer telomeres, protein caps on the end of chromosomes that get shorter with age. Although there are only a few studies on this topic and more research is needed, “the findings are promising in offering a direct tie from psychological well-being to aging and health at the cellular level,” the authors wrote.

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