Objectives. Evidence concerning physical activity and mental health remains less well documented for children and adolescents. An updated review of systematic reviews and meta-analyses was undertaken concerning physical activity and mental health in children and adolescents, and to judge the extent to which associations can be considered causal. Methods. Systematic reviews and meta-analyses were identified to update our previous review of reviews (Biddle & Asare, 2011), with papers identified between November 2010 and the end of 2017. Criteria were used to judge causality (Hill, 1965), including strength of association, dose-response association, and experimental evidence. Results. Since 2011, the quantity (k=42 reviews) and quality of research has increased in depression (evidence from 10 reviews), self-esteem (10 reviews) and cognitive functioning (25 reviews). Anxiety had only three new, small, reviews. Intervention effects for depression are moderate in strength while observational data show only small or null associations. Variable effect sizes are evident from interventions for the reduction of anxiety and improvement in self-esteem. Higher or improved fitness and physical activity are associated with better cognitive health and performance. There was partial support for a causal association with depression, a lack of support for self-esteem, but support for cognitive functioning. Conclusions. There are significant increases in research activity concerning physical activity and depression, self-esteem, and cognitive functioning in young people. The strongest evidence for a causal association appears to be for cognitive functioning, and there is partial evidence for depression.

BackgroundThe current Australia's Physical Activity and Sedentary Behaviour Guidelines recommend that adults engage in regular moderate-to-vigorous-intensity physical activity (MVPA) and strength training (ST), and minimise time spent in sedentary behaviours (SB). However, evidence about the specific individual and concurrent distribution of these behaviours in Australia is scarce. Therefore, the aim of this study was to determine the prevalence and sociodemographic correlates of MVPA, ST and SB in a national-representative sample of Australian adults.MethodsData were collected using face-to-face interviews, as part of the National Nutrition and Physical Activity Survey 2011–12. The population-weighted proportions meeting the MVPA (≥150 min/week), ST (≥2 sessions/week) and combined MVPA-ST guidelines, and proportions classified as having ‘low levels of SB’ (<480 min/day) were calculated, and their associations with selected sociodemographic and health-related variables were assessed using multiple logistic regression analyses. This was also done for those at potentially ‘high-risk’, defined as insufficient MVPA-ST and ‘high-sedentary’ behaviour.ResultsOut of 9345 participants (response rate = 77.0 %), aged 18–85 years, 52.6 % (95 % CI: 51.2 %–54.0 %), 18.6 % (95 % CI: 17.5 %–19.7 %) and 15.0 % (95 % CI: 13.9 %–16.1 %) met the MVPA, ST and combined MVPA-ST guidelines, respectively. Female gender, older age, low/medium education, poorer self-rated health, being classified as underweight or obese, and being a current smoker were independently associated with lower odds of meeting the MVPA, ST and combined MVPA-ST guidelines. A total of 78.9 % (95 % CI: 77.9 %–80.0 %) were classified as having low levels of SB. Females, older adults and those with lower education were more likely to report lower levels of SB, whilst those with poor self-rated health and obese individuals were less likely to report lower levels of SB (i.e. SB = ≥480 min/day). A total of 8.9 % (95 % CI: 8.1 %–9.6 %) were categorised as individuals at potentially ‘high-risk’. Those with poorer self-rated health, obese individuals, those aged 25–44, and current smokers were more likely to be in the ‘high risk’ group.ConclusionsThe large majority of Australian adults do not meet the full physical activity guidelines and/or report excessive SB. Our results call for public health interventions to reduce physical inactivity and SB in Australia, particularly among the subgroups at the highest risk of these unhealthy behaviours.

Available evidence is generally not supportive of associations between sedentary behaviour and obesity in adults. Most studies that found significant associations indicated mostly small effect sizes. Somewhat more consistent associations were shown for screen time (mainly TV viewing), among older adults, and for pre-adult sedentary behaviour to increase the risk of obesity in adulthood. Some evidence also exists for breaks in sedentary time to be associated with a more favourable BMI, and for use of a car to be associated with greater risk of obesity. There is limited evidence for an association between sedentary behaviour in adulthood and obesity and any association that exists does not seem to be causal. Future research is required investigating potentially positive effects for frequent breaks from sitting, less car use, and an uncoupling of TV viewing and dietary intake.

Accumulating high volumes of sedentary behaviour is a risk factor for multiple negative health-related outcomes. The objective of this review was to synthesise the evidence on the levels of sedentary behaviour in university students. Screened records from 13 databases were included if (i) published after 2007 and (ii) reported on university students' amount of total or domain-specific sedentary behaviour. Sub-group and meta-regression analyses were conducted to investigate potential sources of heterogeneity (moderators). A total of 125 studies met the inclusion criteria. Most studies were cross-sectional (84%) and reported screen time (61%) or total sedentary time (39%). Self-reported data indicated that university students spend 7.29 h per day being sedentary. The levels of total sedentary behaviour were significantly higher when measured with accelerometers (M = 9.82 h per day). Computer use presented significantly higher prevalence over other modalities of screen time. Among the explored factors (i.e. countries' income, age, gender, and study's publication date), only publication date significantly moderated sedentary behaviour. Results suggest that a considerable proportion of university students (i) engage in higher levels of sedentary time compared to the general young adult population and (ii) accumulate levels of sedentary time that have been associated with an increased risk for detrimental health outcomes. In addition, meta-regression analyses suggest that sedentary time has increased over the last 10-year period among university students. These findings may inform future initiatives and policies targeting university students' sedentary behaviour. Further research is needed to identify the factors moderating sedentary behaviour in the university setting.