Lifestyle Behaviours as Predictors of Health: Understanding the Importance of Sleep, Diet and Physical Activity on Mental Health and Well-Being
There is now considerable evidence supporting the notion that sleep, diet, and physical activity can benefit mental health and well-being individually. Previous literature suggests young adults who sleep between seven- to nine-hours-per-night have reduced depressive symptoms and anxiety, along with elevated mood, when compared to participants sleeping fewer than seven or greater than nine hours per night. Furthermore, following a healthy diet has also been associated with improvements in mood and well-being, whereby individuals who regularly adhere to a Mediterranean diet show elevated mood and a reduced risk of depression. Finally, regular physical activity has also been associated with greater mental health and well-being, whereby regular aerobic exercise at moderate intensity has been shown to reduce symptoms of major depressive disorder and anxiety. However, health behaviours do not occur in isolation, and instead tend to cluster together. Yet, research considering the way all three behaviours combine to predict mental health and well-being is still in its infancy. Therefore, the aim of the present thesis was to investigate the combined relationship between sleep, diet and physical activity in predicting mental health and well being outcomes, in two separate cross-sectional studies, both with young adults aged 17-25 years old. Study 1 was a large scale, cross-sectional survey of 1533 participants from New Zealand and the United States. Study 2 was a 13-day micro-longitudinal survey based study of 783 participants from New Zealand. Both studies measured multiple self-reported lifestyle behaviours, such as sleep quality and quantity, consumption of fruit and vegetables, and physical activity habits, along with several measures of mental health (depressive symptoms and negative mood) and well-being (life satisfaction, flourishing and positive mood). Study 1 also measured anxiety and vitality. Results of Study 1 supported past research, that when tested in isolation, each health behaviour was associated with greater mental health and well being. However, when tested against each other in regression models, sleep quality was the strongest predictor of all mental health and well-being outcomes. Diet and physical activity were weaker, relatively equal and still statistically significant predictors. Two trends were observed where raw fruit and vegetable consumption moderated the relationship between sleep quality, and both vitality and flourishing. Study 2 showed similar results, where each health behaviour was associated with greater mental health and well-being when tested in isolation. Furthermore, when tested against each other in regression models, sleep quality was again the strongest predictor of all mental health and well-being outcomes. Both diet and physical activity were relatively equal, weak predictors of mental health and well-being. No significant moderation effects were observed. These results suggest that sleep quality may be the strongest predictor of mental health and well-being, meaning intervention research should focus on sleep quality interventions among young adults.
Advisor: Conner, Tamlin
Degree Name: Master of Science
Degree Discipline: Psychology
Publisher: University of Otago
Keywords: well being; sleep quality; physical activity; diet; health behaviours
Research Type: Thesis