Mental well-being is influenced by several lifestyle factors, but they're not all created equal.

We know that a complex combination of behaviors and lifestyle factors influence our mental health and overall well-being, and that physical and mental health are inherently connected. So just as healthy habits around sleep, diet, and exercise—dubbed the “big three” healthy lifestyle factors—are all vital to staying in top form physically, they also correlate significantly with mental health. Research has found that eating well, getting regular exercise, and making sure to clock enough high-quality sleep each night can help boost psychological well-being and reduce the risk of conditions like depression and anxiety. And conversely, deficiencies in any or all of these behaviors can negatively impact mood and outlook.

Everyone should aim to eat, move, and snooze for the betterment of their body and mind (for the most part, anyway—an occasional slice of cake is arguably also extremely important for mental health). But of these three factors, sleep appears to be the strongest predictor of mental well-being, according to research published in Frontiers in Psychology—and, more specifically, sleep quality, followed closely by sleep quantity. This suggests that, while you should, of course, prioritize all three for optimal health and longevity, taking extra care to work on your sleep habits could be the most beneficial strategy or keeping your spirits high and minimizing stress, worry, and mood dips.

For this cross-sectional analysis of sleep, diet, and physical activity’s individual and collective relationship to mental well-being in young adults, researchers from the department of psychology at the University of Otago, in Dunedin, New Zealand, surveyed more than 1,100 young men and women from New Zealand and the U.S. Participants were given an online survey measuring their sleep, exercise, and nutritional habits; as well as the “outcome measures of depressive symptoms, measured by the Center for Epidemiological Depression Scale (CES-D), and well-being (measured by the Flourishing Scale).” 

sleep-exercise-diet-mental-health-study: woman closing eyes
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Controlling for covariates—varying characteristics like demographics, ethnicity, body mass index, and health conditions among survey-takers—the results revealed that sleep quality, or how well they sleep, followed closely by sleep quantity, or how much they sleep, were the largest indicators both of participants’ depression levels and their overall well-being, or “flourishing.” (Inadequate, shallow, and/or interrupted sleep, for instance, has been associated with increased risk of mood disorders, addiction, and emotion regulation in adolescents.) According to the published paper, “Individuals who slept inside the range of 8 to 12 hours per night (not more or less) and who had better sleep quality reported fewer depressive symptoms.” 

Falling just behind sleep is physical activity, the second highest predictor of depressive symptoms. Exercise releases endorphins that help raise your spirits and boost energy, and regular physical activity has been shown to help treat depression and anxiety. On the other hand, lack of activity is associated with poorer mental health in young adults. Diet, though crucial, appeared to be the weakest indicator of depressive symptoms and low well-being out of the three. “Only one dietary factor—raw fruit and vegetable consumption—predicted greater well-being, but not depressive symptoms when controlling for covariates,” the authors noted.

It’s important to note that since these measurements were self-reported via survey and only observed, not changed or tested in any way, all results are purely correlational rather than causal. But the patterns revealed in the analysis offer intriguing insight into the potential hierarchy of modifiable lifestyle behaviors. Going forward, these findings may help guide future research and treatment for mood disorders to focus on maximizing sleep quality to improve mental health, particularly in adolescents. 

As for how this affects you? Take this as yet another reminder not to skimp on valuable sleep, keep up that steady fitness routine, and eat as many fresh, unprocessed foods as you can.