The transition to university relates to marked shifts in social, academic, and financial demands [1, 2], and adjustments to these new demands may be linked to lifestyle behavior changes [3]. These changes are well documented, showing university students often present high levels of physical inactivity [4] and sedentary behavior [5], poor and unbalanced diet [3], high rates of alcohol and other substance misuse [6], poor sleep patterns [7], and longer screen time [8].
Lifestyle behaviors may constitute modifiable risk or protective factors for the emergence of mental health symptoms [9]. For example, high physical inactivity levels, poor diet, poor sleep quality, substance misuse, and long screen exposure increase the risk for incident mental health symptoms [10–18]. However, most studies to date have only evaluated the association between isolated lifestyle behaviors and mental health symptoms (e.g., sleep and depression) [10–18]. Lifestyle behaviors do not occur in isolation, but are often clustered [11–20]. Among university students, higher levels of physical activity cluster with better dietary habits and less smoking [21, 22]. On the other hand, higher levels of physical activity may cluster with increased alcohol consumption [22], while sedentary behavior is associated with poor sleep but not with smoking [23]. Considering the nature of cluster formations among multiple lifestyle behaviors, it is plausible that examining an individual's multiple lifestyle behaviors can provide a person-centered approach to explain the associations between lifestyle behaviors and mental health symptoms [24].
Some evidence suggests that clusters of lifestyle behaviors are associated with mental health in university students [25–33]. In Australian students [27], four distinct clusters were identified: “healthiest”, “healthy”, “mixed”, and “sedentary and distressed”. The "healthiest" cluster (higher levels of physical activity and fruit consumption, less binge drinking, and the least sedentary behavior) showed the lowest levels of depression, anxiety, and stress compared to the other clusters. Another study with Australian students found three clusters: “healthier”, “moderate”, and “unhealthier” lifestyles, with the last two being associated with a higher risk of psychological distress [25]. In Chinese students [31], four clusters were identified: 1) active pattern (those with higher levels of physical activity); 2) high sleep duration pattern; 3) high screen time pattern; and 4) low-physical activity-low-sleep duration pattern. The study found that those with low physical activity and low sleep duration were at increased risk for depressive symptoms. Notwithstanding the above, this evidence derives from cross-sectional studies, providing no evidence of the temporality of the association.
The Seguimiento Universidad de Navarra (SUN) cohort is one of few prospective studies showing that students with ten healthy lifestyle behaviors, named as the "healthier lifestyle" cluster (i.e., classified as healthy across ten lifestyle behaviors: smoking, physical activity, diet, body mass index, alcohol consumption, television exposure, binge-drinking binge, afternoon nap, time spent with friends and working) had a 32% reduced risk of developing depression compared to those reporting three or less healthy behaviors [33]. Nonetheless, this evidence is limited to depression, hence preventing the generalization of results to other mental health symptoms.
Lifestyle behaviors and mental health symptoms are related to contextual factors such as cultural and social factors [34, 35]. There is literature suggesting that some lifestyle behaviors are universal protective factors for some mental health symptoms[15, 36], while others may be context-specific. For example, physical activity is a universal protective factor against depression and anxiety, with no significant variation in the magnitude of the effect size between geographical regions [15, 36]. On the other hand, alcohol consumption is prospectively associated with “positive mental health” and a lower frequency of depression, anxiety, and stress in German students, but with a higher frequency of depression, anxiety, and stress in Chinese students [36]. However, this evidence relies on data from two countries and a limited set of behaviors (physical and mental activity, alcohol consumption, smoking, circadian and social regularity). Further studies in multiple countries and evaluating a broader set of lifestyle behaviors are needed to understand the universal and country-specific associations.
Lifestyle behaviors and mental health vary during university years. Data from the Household, Income, and Labour Dynamics study (HILDA) demonstrated that mental health has a time-varying course in Australian students [37]. In this cohort, young university students experienced a reduction in mental health from 16 to 17 years, then an increase from age 17 to 18, then a reduction again from age 19 to 20, and then an increase from age 20 to 21. In a sample of UK students, four different trajectories were identified: persistent high-severity symptoms, varying opposed to national variation, varying consistently with national variation, and persistent to low severity [38]. Similarly, lifestyle behaviors seem to have varying trajectories over time [39, 40]. However, there is a paucity of prospective studies investigating the associations between lifestyle behavior and mental health trajectories in a large cohort of university students.
Given the aforementioned lack of prospective studies investigating the association of multiple lifestyle behaviors with multiple mental health symptoms in a diverse international cohort of universithy students, the UNIversity students’ LIFEstyle and Mental health (UNILIFE-M) was designed and conceived. The UNILIFE-M cohort is a large multicenter, international, prospective cohort study that aims to provide an intricated view of the dynamic associations between multiple lifestyle behaviors (physical activity, sedentary behavior, diet, stress management, sleep, substance consumption, exposure to green environment, and social support), either in an independent or clustering manner, and a broad scope of mental health symptoms (depressive, anxiety, manic, obsessive-compulsive, psychotic, or attention-deficit/hyperactivity symptoms, substance abuse, or suicidal ideation), in an international cohort of university students.