Making the right moves to prevent depression in young people
Authors: Karmel W Choi, Jordan W Smoller
Journal: The Lancet Psychiatry (2020)

Adolescence is a key window of vulnerability for depression, the leading cause of disability worldwide. The prevention of depression among young people is therefore of substantial public health importance. A growing body of large-scale data now supports the conclusion that physical activity is associated with a reduced risk of depression1Schuch FB Vancampfort D Firth J et al.Physical activity and incident depression: a meta-analysis of prospective cohort studies.Am J Psychiatry. 2018; 175: 631-648Crossref PubMed Scopus (339) Google Scholar, 2Choi KW Chen C-Y Stein MB et al.Assessment of bidirectional relationships between physical activity and depression among adults: a 2-sample mendelian randomization study.JAMA Psychiatry. 2019; 76: 399-408Crossref PubMed Scopus (106) Google Scholar and thus serves as a promising prevention target. However, few studies have focused on adolescents and, of these, many are cross-sectional and have relied on self-report measures of physical activity that might poorly capture the full range of relevant activities over time. In The Lancet Psychiatry, Kandola and colleagues3Kandola A Lewis G Osborn DPJ Stubbs B Hayes JF Depressive symptoms and objectively measured physical activity and sedentary behaviour throughout adolescence: a prospective cohort study.Lancet Psychiatry. 2020; (published online Feb 11.)https://doi.org/10.1016/S2215-0366(20)30034-1Scopus (35) Google Scholar draw on a prospective population-based cohort from which objective measures of physical activity were collected4Mattocks C Ness A Leary S et al.Use of accelerometers in a large field-based study of children: protocols, design issues, and effects on precision.J Phys Act Health. 2008; 5: S98-S111Crossref PubMed Scopus (266) Google Scholar at three different timepoints (around 12 years, 14 years, and 16 years of age) to provide the most fine-grained characterisation to date of physical activity patterns across adolescence and their implications for depression. Between 12 years and 16 years of age, mean time spent in sedentary behaviour increased by more than 90 min/day—from about 7·2 h/day (SD 1·1) to 8·7 h/day (1·1). A 60 min/day increase in sedentary behaviour at any of the three timepoints was associated with an 8–11% higher depression score at 18 years of age. Notably, this risk appeared to be driven by the displacement of light physical activity: decreases in the amount of light activity directly mirrored increases in sedentary behaviour between 12 years and 16 years of age, and each 60 min/day increase in light activity was associated with a lower depression score at 18 years, with effects that were opposite and roughly equal in magnitude to those of sedentary behaviour. Findings persisted when adjusting for baseline depressive symptoms or when excluding individuals with elevated baseline symptoms, and even when considering depression as a binary outcome. Notably, moderate-to-vigorous physical activity, which has been the focus of most previous studies, had a less consistent association with depression compared with those of light activity or sedentary behaviour. Adolescents are known to become less active over time,5Dumith SC Gigante DP Domingues MR Kohl HW Physical activity change during adolescence: a systematic review and a pooled analysis.Int J Epidemiol. 2011; 40: 685-698Crossref PubMed Scopus (696) Google Scholar for multifactorial reasons. The good news from this study is the implication that light activity—which can include movements as simple as standing, stretching, or casual walking—might be an effective strategy for decreasing the burden of adolescent depression. While not able to establish causality, this study's fully prospective analyses and adjustment for a range of plausible confounders strengthen the validity of these findings, which, if supported by further research, could have important implications for expanding recommendations offered to young people. According to WHO physical activity guidelines, adolescents should aim for at least 60 min of moderate-to-vigorous activity each day.6WHOGlobal recommendations on physical activity for health. World Health Organization, Geneva, Switzerland2010https://www.who.int/dietphysicalactivity/publications/9789241599979/en/Date accessed: January 30, 2020Google Scholar Absent from these guidelines, Kandola and colleagues note,3Kandola A Lewis G Osborn DPJ Stubbs B Hayes JF Depressive symptoms and objectively measured physical activity and sedentary behaviour throughout adolescence: a prospective cohort study.Lancet Psychiatry. 2020; (published online Feb 11.)https://doi.org/10.1016/S2215-0366(20)30034-1Scopus (35) Google Scholar are specific recommendations around lighter forms of activity, despite the fact that such activities occupy a substantial portion of waking hours and might be a more amenable starting point for individuals with high levels of sedentary behaviour. To guide future recommendations, more data on the benefits of lower-intensity activities are needed. Objective measures, using accelerometers and other devices, are well suited to capture physical activity across the intensity spectrum. Evidence indicates that objective—but not self-report—measures of physical activity appear to be causally related to depression risk,2Choi KW Chen C-Y Stein MB et al.Assessment of bidirectional relationships between physical activity and depression among adults: a 2-sample mendelian randomization study.JAMA Psychiatry. 2019; 76: 399-408Crossref PubMed Scopus (106) Google Scholar perhaps because of their ability to detect broader forms of movement that are potentially relevant for mental health. There are foreseeable challenges, however, to translating these data into implementable recommendations. The very advantages of light physical activity (eg, easily accumulated in small ways throughout the day) make it harder to monitor and quantify reliably. Presently, there is also between-study heterogeneity in the definitions of light and moderate-to-vigorous activity based on accelerometer outputs. Thus, the question remains how we can pool estimates into comparable metrics to inform robust guidelines. As exhortations to move more and sit less become more common, it is also worth noting that the optimal intensity (and perhaps even duration and types)7Teychenne M White RL Richards J Schuch FB Rosenbaum S Bennie JA Do we need physical activity guidelines for mental health: what does the evidence tell us?.Ment Health Phys Act. 2020; 18100315Crossref Scopus (48) Google Scholar of physical activity might depend on which outcome we are trying to target. More vigorous activity might indeed be most beneficial for physical outcomes such as bone health or adiposity,8Poitras VJ Gray CE Borghese MM et al.Systematic review of the relationships between objectively measured physical activity and health indicators in school-aged children and youth.Appl Physiol Nutr Metab. 2016; 41: S197-S239Crossref PubMed Scopus (706) Google Scholar whereas, for depression, lighter activity might be sufficient or even preferable. One size likely does not fit all: physical activity guidelines and their implementation might require a precision approach. The overall relationship between physical activity and mental health is intuitive and something the general public has perhaps implicitly understood. This study by Kandola and colleagues3Kandola A Lewis G Osborn DPJ Stubbs B Hayes JF Depressive symptoms and objectively measured physical activity and sedentary behaviour throughout adolescence: a prospective cohort study.Lancet Psychiatry. 2020; (published online Feb 11.)https://doi.org/10.1016/S2215-0366(20)30034-1Scopus (35) Google Scholar adds to a now-robust evidence base pointing to physical activity as a potential primary and tertiary prevention strategy for depression. Evidence on the mental health benefits of lighter activity, especially in young people, is also accumulating.9Hamer M Patalay P Bell S Batty GD Change in device-measured physical activity assessed in childhood and adolescence in relation to depressive symptoms: a general population-based cohort study.J Epidemiol Community Health. 2020; (published online Jan 23.)DOI:10.1136/jech-2019-213399Crossref Scopus (3) Google Scholar Changing behaviour to align with this evidence is the next frontier. Identifying major drivers of sedentary behaviour in adolescents, as well as potential sources of light activity in their daily lives, could enhance the design of targeted prevention strategies. For now, the data suggest that, when it comes to depression, a broad spectrum of physical movement—including light activity—is probably the right move. KWC has received grant funding from the National Institute of Mental Health. JWS has received grant funding from the Demarest Lloyd Jr Foundation, is an unpaid member of the Bipolar/Depression Research Community Advisory Panel of 23andMe, and is a member of the Leon Levy Foundation Neuroscience Advisory Board. Depressive symptoms and objectively measured physical activity and sedentary behaviour throughout adolescence: a prospective cohort studySedentary behaviour displaces light activity throughout adolescence, and is associated with a greater risk of depressive symptoms at 18 years of age. Increasing light activity and decreasing sedentary behaviour during adolescence could be an important target for public health interventions aimed at reducing the prevalence of depression. Full-Text PDF Open Access