Better sleep quality and healthy habits linked to improved mental wellbeing in young adults

A new study of young adults has strongly linked better sleep quality with better mental wellbeing, with fruit and vegetable consumption and physical activity also strongly associated with psychological wellbeing. Perhaps surprisingly, the findings also suggest that boosting fruit and vegetable intake could potentially help mitigate the effects on wellbeing of a poor night's sleep. Dr. Jack Cooper, previously from the University of Otago, New Zealand, and colleagues present these findings in the open-access journal PLOS One on August 27, 2025.

Prior research has linked better health behaviors-actions that people can adjust in their lives-to better physical health. Evidence also suggests that health behaviors may be linked to mental wellbeing. However, research on this topic has been limited. For example, studies have typically focused only on mental illness, a separate measure from positive psychological wellbeing, and they typically neglect to consider how different health behaviors might interact to affect wellbeing.

To address these and other gaps, Cooper and colleagues analyzed relationships between three health behaviors-sleep quality, eating fruits and vegetables, and physical activity-and psychological wellbeing in adults aged 17 to 25. They used data from three studies: a survey study of 1,032 adults in New Zealand, the U.K., and the U.S.; a 13-day study of 818 New Zealand adults who were asked to keep a daily diary; and an 8-day diary study of 236 New Zealand adults who also wore Fitbits tracking physical activity.

Across all three studies, better sleep quality was most strongly associated with better mental wellbeing, with fruit and vegetable consumption coming in second. Both behaviors showed benefits even when comparing between different days for the same person – so eating more fruit and vegetables one day was associated with a real-time wellbeing boost. Physical activity – whether measured by FitBits or diaries, which aligned – was also linked to better wellbeing, but mostly when comparing between days for an individual rather than when comparing across individuals.

Links between each of the three behaviors and wellbeing appeared to be independent and additive - which might mean that the more of them you do, the bigger the wellbeing benefit. The only exception: above-average intake of fruits and vegetables appeared to mitigate the effects of a poor night's sleep, and a good night's sleep appeared to protect against lower fruit and vegetable intake.

This study used samples of young adults from three countries-the U.K., U.S., and New Zealand-and samples sizes were relatively homogeneous. Future research could address some of these limitations by including participants from additional countries and increasing the sample size to improve generalizability. Although this study could not prove a causative link between these behaviors and mental wellbeing, the authors hope that their findings could inform efforts to improve psychological wellbeing of young adults.

Young adults don't have to reach some objective benchmark of healthiness to see wellbeing improvement. Sleeping a little better, eating a little healthier, or exercising even for 10 minutes longer than you normally do was associated with improvements to how you feel that day."

Dr. Jack Cooper, Lead Author

Senior author Professor Tamlin Conner, of the University of Otago Psychology Department, adds: "Understanding what lifestyle factors support wellbeing can help young adults not just 'get by' but thrive during this critical life stage."

"Of these healthy habits, sleep quality stood out as the strongest and most consistent predictor of next-day wellbeing, but eating fruit and vegetables and being active also helped boost wellbeing".

"This age group faces unique pressures – such as leaving home, financial stress, educational pressures and social stressors – that can lower happiness. Understanding what lifestyle factors support wellbeing can help young adults not just 'get by' but thrive during this critical life stage.