Sleep quality strongest predictor of daily wellbeing in young adults

A new analysis of nearly 2,100 young adults found that better sleep quality was the strongest and most consistent predictor of day-to-day psychological wellbeing, with higher fruit and vegetable intake and increased physical activity also associated with improved mood, researchers reported on Aug. 27, 2025. The findings, from investigators at the University of Otago in New Zealand and published in PLOS One, suggest modest changes in everyday habits may boost how young people feel from one day to the next.

Researchers pooled data from three studies involving adults aged 17 to 25: a cross‑national survey of 1,032 participants in New Zealand, the United Kingdom and the United States; a 13‑day daily diary study of 818 New Zealanders; and an eight‑day diary study of 236 New Zealanders who also wore Fitbits to track activity. Across all three datasets, sleep quality showed the strongest association with next‑day wellbeing. Fruit and vegetable consumption ranked second, and physical activity was linked to better wellbeing primarily when comparisons were made within individuals across days rather than between different people.

Lead author Jack Cooper said small, achievable changes...