Assessment of Bidirectional Relationships Between Physical Activity and Depression Among Adults: A 2-Sample Mendelian Randomization Study

Physical activity, sedentary, and dietary behaviors associated with indicators of mental health and suicide risk

We used data from the 2017 national Youth Risk Behavior Survey to examine associations between physical activity, sedentary, and healthy dietary behaviors and indicators of mental health, suicidal thoughts, and suicidal attempts among a representative sample of US high school students. Sex-stratified logistic regression was used to separately model each mental health-related outcome on the health-related behaviors, while controlling for race/ethnicity, grade, and body weight status. Significant associations were found between insufficient physical activity, sedentary, and less healthy dietary behaviors and the mental health-related outcomes. Feeling sad and hopeless was associated with not eating breakfast on all 7 days (past week), drinking soda or pop (female only), not meeting the aerobic physical activity guideline (male only), not playing on at least one sports team, and playing video/computer games or using a computer more than two hours (per day). Suicidal thoughts were associated with not eating breakfast on all 7 days, drinking soda or pop, not meeting the aerobic physical activity guideline, and playing video/computer games or using a computer more than two hours per day. Attempted suicide was associated with not eating breakfast on all 7 days, drinking soda or pop, drinking sports drinks, watching television more than two hours per day, and playing video or computer games or using a computer more than two hours per day (male only). While limiting sedentary behaviors and increasing physical activity and healthy dietary behaviors is not a sole solution for improving mental health among adolescents, it could be another possible strategy used in schools to benefit all students.

Physical Activity and Body Composition Are Associated With Severity and Risk of Depression, and Serum Lipids

BACKGROUND

Physical activity and a healthy body composition are said to reduce the risk of major depressive disorder. Nonetheless, deeper insight is needed into which specific forms of physical activity (and their relation to body composition) are effective in improving and preventing depressive symptoms.

METHODS

We compared different self-reported physical activities of the Global Physical Activity Questionnaire and body composition measures between patients with a current major depressive episode (MDE; N = 130) and healthy control subjects (N = 61). These parameters were also tested for correlations with depression severity and serum lipid levels in patients and controls.

RESULTS

Patients with a current MDE reported significantly fewer hours spent on total physical activity, walking or bicycling for travel, and vigorous-intensity activities at leisure than healthy control subjects. More time spent on vigorous-intensity activities at work, less time spent on walking or bicycling for travel, higher body fat mass, and lower body muscle mass correlated significantly with stronger depression severity. Physical activity and body measures correlated significantly with serum lipid levels.

LIMITATIONS

Self-reports of physical activity, only short-term follow-up of 20 days, cross-sectional study design without examination of causal role of exercise.

CONCLUSIONS

More time spent on traveling by foot or by bike is especially associated with a lower risk of and milder depression. These results highlight the differential role of physical activity in depression.

Measurement properties of smartphone approaches to assess key lifestyle behaviours: protocol of a systematic review

BACKGROUND

Six core behavioural risk factors (poor diet, physical activity, sedentary behaviour, alcohol misuse, smoking and unhealthy sleep patterns) have been identified as strong determinants of chronic disease, such as cardiovascular disease, diabetes and cancers. Smartphones have the potential to provide a real-time, pervasive, unobtrusive and cost-effective way to measure health behaviours and deliver instant feedback to users. Despite this, validity of using smartphones to measure these six key behaviours is largely unknown. The proposed systematic review aims to address this gap by identifying existing smartphone-based approaches to measure these health behaviours and critically appraising, comparing and summarizing the quality of their measurement properties.

METHODS

A systematic search of the Ovid MEDLINE, Embase (Elsevier), Cochrane Library (Wiley), PsychINFO (EBSCOhost), CINAHL (EBSCOHost), Web of Science (Clarivate), SPORTDiscus (EBSCOhost) and IEEE Xplore Digital Library databases will be conducted from January 2007 to March 2020. Eligible studies will be those written in English that measure at least one of the six health behaviours of interest via a smartphone and report on at least one measurement property. The primary outcomes will be validity, reliability and/or responsiveness of these measurement approaches. A secondary outcome will be the feasibility (e.g. user burden, usability and cost) of identified approaches. No restrictions will be placed on the participant population or study design. Two reviewers will independently screen studies for eligibility, extract data and assess the risk of bias. The study methodological quality (or bias) will be appraised using an appropriate tool. Our results will be described in a narrative synthesis. If feasible, random effects meta-analysis will be conducted where appropriate.

DISCUSSION

The results from this review will provide important information about the types of smartphone-based approaches currently available to measure the core behavioural risk factors for chronic disease and the quality of their measurement properties. It will allow recommendations on the most suitable and effective measures of these lifestyle behaviours using smartphones. Valid and reliable measurement of these behaviours and risk factor opens the door to targeted and real-time delivery of health behaviour interventions, providing unprecedented opportunities to offset the trajectory toward chronic disease.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO: CRD42019122242.

The association between physical fitness and mental health in Norwegian adolescents

BACKGROUND

Studies indicate that health-related components of physical fitness are associated with mental health outcomes. However, research is scarce concerning this relationship in young adolescents in general and non-existent in Norwegian populations specifically. The aim of the study was to examine whether body composition, muscular strength and cardiorespiratory fitness were associated with self-reported mental health in Norwegian adolescents.

METHODS

Adolescents from four regions of Norway (n = 1486; mean age = 13.9; girls = 50.6%) participated. Self-reported mental health (psychological difficulties) was measured by completing the Strengths and Difficulties Questionnaire. Cardiorespiratory fitness was assessed with an intermittent running test; muscular strength was assessed by measuring handgrip strength, standing broad jump and sit-ups; and body composition was assessed by calculating body mass index from weight and height. Linear mixed effects models were conducted to assess the associations between the health-related components of physical fitness and psychological difficulties. School clusters were included as random effects and all models were controlled for sex, socioeconomic status and birthplace (domestic or foreign).

RESULTS

Body composition was not associated with psychological difficulties. Muscular strength was independently associated with psychological difficulties, but when all independent variables were entered in the fully adjusted model, only cardiorespiratory fitness was associated with psychological difficulties.

CONCLUSIONS

There was a small but significant inverse association between cardiorespiratory fitness and levels of psychological difficulties in Norwegian adolescents. The results suggest that muscular strength is not associated with psychological difficulties in adolescents, when controlling for cardiorespiratory fitness. Future research should focus on the prospective association between physical fitness components and mental health outcomes in adolescents.

TRIAL REGISTRATION

The study is registered in ClinicalTrials.gov ID nr: NCT03817047. Retrospectively registered January 25, 2019.

Effects of Exercise on Brain and Cognition Across Age Groups and Health States

Exercise has been shown to benefit brain structure and function, particularly in aging populations. However, the mechanisms by which exercise exerts its effects, especially in humans, are not fully understood. This review argues that one reason for this knowledge gap is that exercise likely operates through multiple levels of mechanisms. Furthermore, the mechanisms of exercise may vary depending on factors such as age and health state. We discuss the state of evidence at each of three levels of analysis (molecular/cellular, brain structure/function, and mental states and higher-order behaviors) and highlight consistencies across these levels, inconsistencies within them, and knowledge gaps. Lastly, based on these, we speculate about which mechanisms of exercise may be universal across age groups and populations versus those that might be distinct to specific age ranges or populations.

Association of physical activity, sedentary behaviours and sleep duration with cardiovascular diseases and lipid profiles: a Mendelian randomization analysis

Background

Observational studies have shown that moderate-to-vigorous physical activity (MVPA), vigorous physical activity (VPA), sedentary behaviours, and sleep duration were associated with cardiovascular diseases (CVDs) and lipid levels. However, whether such observations reflect causality remain largely unknown. We aimed to investigate the causal associations of physical activity, sedentary behaviours, and sleep duration with coronary artery disease (CAD), myocardial infarction (MI), stroke and lipid levels.

Methods

We conducted a Mendelian randomization (MR) study using genetic variants as instruments which are associated with physical activity, sedentary behaviours, and sleep duration to examine the causal effects on CVDs and lipid levels. This study included analyses of 4 potentially modifiable factors and 7 outcomes. Thus, the threshold of statistical significance is P = 1.8 × 10^− 3 (0.05/4 × 7) after Bonferroni correction.

Results

In the present study, there was suggestive evidence for associations of genetically predicted VPA with CAD (odds ratio, 0.65; 95% confidence intervals, 0.47–0.90; P = 0.009) and MI (0.74; 0.59–0.93; P = 0.010). However, genetically predicted VPA, MVPA, sleep duration and sedentary behaviours did not show significant associations with stroke and any lipid levels.

Conclusions

Our findings from the MR approach provided suggestive evidence that vigorous exercise decreased risk of CAD and MI, but not stroke. However, there was no evidence to support causal associations of MVPA,sleep duration or sedentary behaviours with cardiovascular risk and lipid levels.

Translational perspective

The findings of this study did not point out specific recommendations on increasing physical activity required to deliver significant health benefits. Nevertheless, the findings allowed clinicians and public health practitioners to provide advice about increasing the total amount of excising time by demonstrating that such advice can be effective. Reliable assessment of the association of physical activity levels with different subtypes of CVDs is needed to provide the basis for a comprehensive clinical approach on CVDs prevention, which can be achieved through lifestyle interventions in addition to drug therapy.

Effectiveness of universal multiple-risk lifestyle interventions in reducing depressive symptoms: Systematic review and meta-analysis

Though many studies have explored the association between single-risk lifestyle interventions and depression, unhealthy lifestyle factors often co-occur, with adults engaging in two or more risk behaviours. To date, little is known about the effectiveness of universal multiple-risk lifestyle interventions to reduce depressive symptoms. We conducted a SR/MA to assess the effectiveness of universal multiple-risk lifestyle interventions (by promoting a healthy diet, physical activity and/or smoking cessation) to reduce depressive symptoms in adults. We searched MEDLINE, Scopus, CENTRAL, PsycINFO, WOS, OpenGrey, the ICTRP and other sources from inception to 16 September 2019. We selected only randomized controlled trials, with no restrictions on language or setting. Our outcome was the reduction of depressive symptoms. We calculated the standardized mean difference using random-effect models. Sensitivity, sub-group and meta-regression analyses were performed. Of the 9386 abstracts reviewed, 311 were selected for full-text review. Of these, 23 RCTs met the inclusion criteria, including 7558 patients from four continents. Twenty RCTs provided valid data for inclusion in the meta-analysis. The pooled SMD was -0.184 (95% CI, -0.311 to -0.057; p = 0.005). We found no publication bias, but heterogeneity was substantial (I² = 72%; 95% CI: 56% to 82%). The effectiveness disappeared when only studies with a low risk of bias were included. The quality of evidence according GRADE was low. Although a small preventive effect was found, the substantial heterogeneity and RCTs with lower risk of bias suggested no effectiveness of universal multiple-risk lifestyle interventions in reducing depressive symptoms in a varied adult population. Further evidence is required.

Mobile and wearable technology for monitoring depressive symptoms in children and adolescents: A scoping review

BACKGROUND

There has been rapid growth of mobile and wearable tools that may help to overcome challenges in the diagnosis and prediction of Major Depressive Disorder in children and adolescents, tasks that rely on clinical reporting that is inherently based on retrospective recall of symptoms and associated features. This article reviews more objective ways of measuring and monitoring mood within this population.

METHODS

A scoping review of peer-reviewed studies examined published research that employs mobile and wearable tools to characterize depression in children and/or adolescents. Our search strategy included the following terms: (1) monitoring or prediction (2) depression (3) mobile apps or wearables and (4) children and youth (including adolescents), and was applied to five databases.

RESULTS

Our search produced 829 citations (2008- Feb 2019), of which 30 (journal articles, conference papers and abstracts) were included in the analysis, and 2 reviews included in our discussion. The majority of the evidence involved smartphone apps, with very few studies using actigraphy. Mobile and wearables captured a variety of data including unobtrusive passive analytics, movement and light data, plus physical and mental health data, including depressive symptom monitoring. Most studies also examined feasibility.

LIMITATIONS

This review was limited to published research in the English language. The review criteria excluded any apps that were mainly treatment focused, therefore there was not much of a focus on clinical outcomes.

CONCLUSIONS

This scoping review yielded a variety of studies with heterogeneous populations, research methods and study objectives, which limited our ability to address our research objectives cohesively. Certain mobile technologies, however, have demonstrated feasibility for tracking depression that could inform models for predicting relapse.

Assessing physical activity in people with mental illness: 23-country reliability and validity of the simple physical activity questionnaire (SIMPAQ)

BACKGROUND

Physical inactivity is a key contributor to the global burden of disease and disproportionately impacts the wellbeing of people experiencing mental illness. Increases in physical activity are associated with improvements in symptoms of mental illness and reduction in cardiometabolic risk. Reliable and valid clinical tools that assess physical activity would improve evaluation of intervention studies that aim to increase physical activity and reduce sedentary behaviour in people living with mental illness.

METHODS

The five-item Simple Physical Activity Questionnaire (SIMPAQ) was developed by a multidisciplinary, international working group as a clinical tool to assess physical activity and sedentary behaviour in people living with mental illness. Patients with a DSM or ICD mental illness diagnoses were recruited and completed the SIMPAQ on two occasions, one week apart. Participants wore an Actigraph accelerometer and completed brief cognitive and clinical assessments.

RESULTS

Evidence of SIMPAQ validity was assessed against accelerometer-derived measures of physical activity. Data were obtained from 1010 participants. The SIMPAQ had good test-retest reliability. Correlations for moderate-vigorous physical activity was comparable to studies conducted in general population samples. Evidence of validity for the sedentary behaviour item was poor. An alternative method to calculate sedentary behaviour had stronger evidence of validity. This alternative method is recommended for use in future studies employing the SIMPAQ.

CONCLUSIONS

The SIMPAQ is a brief measure of physical activity and sedentary behaviour that can be reliably and validly administered by health professionals.

Dimensions of leisure-time physical activity and risk of depression in the "Seguimiento Universidad de Navarra" (SUN) prospective cohort

BACKGROUND

An inverse association between total leisure-time physical activity (LTPA) and depression has been previously documented in the scientific literature. Our objective was to prospectively assess the association of LTPA with the risk of depression, focusing on several dimensions of LTPA (intensity, duration and type).

METHODS

The SUN (Seguimiento Universidad de Navarra) project is a prospective cohort study formed by Spanish university graduates. A total of 15,488 adults (40.2% men, mean age 37 ± 12 years) initially free of depression were assessed. A report of a validated medical diagnosis of depression or the habitual use of antidepressants (any of both) were considered as incident cases of depression. LTPA was estimated through previously validated self-reported questionnaires. Participants were classified following Physical Activity recommendations from the World Health Organization, and according to the intensity, duration and type of LTPA. Cox proportional hazards regression models were run, adjusted for demographic, lifestyle, and dietary factors, to estimate adjusted hazard ratios (HR) of depression and 95% confidence intervals (CI).

RESULTS

During 163,059 person-years of follow-up we registered 870 incident cases of depression. Participants with higher total LTPA (METs-h/wk) and higher duration of LTPA (hours/wk) exhibited a lower risk of depression HR = 0.84 (95% CI: 0.72-0.99) and HR = 0.83 (0.70-0.99) respectively, whereas intensity of LTPA (MET) did not show any association with depression.

CONCLUSION

Participants with higher LTPA had a lower risk of depression. The inverse association was stronger for total LPTA time than for its intensity. Higher duration of LTPA should be encouraged to prevent depression.

The causal relationships of device-measured physical activity with bipolar disorder and schizophrenia in adults: A 2-Sample mendelian randomization study

BACKGROUND

To examine the causal association of device-measured physical activity with Bipolar disorder (BIP) and schizophrenia (SCZ) in adults by performing 2-sample MR analysis.

METHODS

Summary-level data for exposure variable including overall physical activity, and three different types of physical activities(sedentary, moderate intensity activity, sleep duration) were derived from UK Biobank(n = 91,105). Summary-level data for outcomes were obtained from Psychiatric Genomics Consortium (PGC) including BIP (n = 51,710) and SCZ(n = 65,967). Cochran's Q statistics, MR-Egger regression, and MR-PRESSO global test were used to identify pleiotropy and MR-PRESSO outlier test for removing the pleiotropy of the genetic instruments. For assessing causality, proven MR techniques including one main analysis(IVW)and four sensitive analysis(MLE,SME,WME, MR-PRESSO)were applied for robust results.

RESULTS

Five MR methods provided consistent genetically evidence that overall physical activity was associated with lower risk of BIP(OR, 0.491; 95% CI: 0.314-0.767; p = 0.002), there was no significant relationship between overall physical activity and SCZ(IVW OR; 1.133; 95% CI: 0.636-2.020; p = 0.672). In addition, no significant causal association was observed between any other types of physical activities and both mental disorders.

LIMITATIONS

The nonlinear association of physical activities on BIP and SCZ were unaccessible through MR analysis.

CONCLUSIONS

This study provides genetic evidence that overall physical activity is an effective preventive factor for BIP but not for SCZ. Together with evidence from observational studies, our finding provides further rationale for individuals at risk for BIP to maintain physical activity.

Physical activity offsets genetic risk for incident depression assessed via electronic health records in a biobank cohort study

BACKGROUND

Physical activity is increasingly recognized as an important modifiable factor for depression. However, the extent to which individuals with stable risk factors for depression, such as high genetic vulnerability, can benefit from the protective effects of physical activity, remains unknown. Using a longitudinal biobank cohort integrating genomic data from 7,968 individuals of European ancestry with high-dimensional electronic health records and lifestyle survey responses, we examined whether physical activity was prospectively associated with reduced risk for incident depression in the context of genetic vulnerability.

METHODS

We identified individuals with incident episodes of depression, based on two or more diagnostic billing codes for a depressive disorder within 2 years following their lifestyle survey, and no such codes in the year prior. Polygenic risk scores were derived based on large-scale genome-wide association results for major depression. We tested main effects of physical activity and polygenic risk scores on incident depression, and effects of physical activity within stratified groups of polygenic risk.

RESULTS

Polygenic risk was associated with increased odds of incident depression, and physical activity showed a protective effect of similar but opposite magnitude, even after adjusting for BMI, employment status, educational attainment, and prior depression. Higher levels of physical activity were associated with reduced odds of incident depression across all levels of genetic vulnerability, even among individuals at highest polygenic risk.

CONCLUSIONS

Real-world data from a large healthcare system suggest that individuals with high genetic vulnerability are more likely to avoid incident episodes of depression if they are physically active.

The effects of aerobic training on subclinical negative affect: A randomized controlled trial

OBJECTIVE

The antidepressant and anxiolytic effects of aerobic exercise are well known, but less is known about its effects on subclinical levels of trait negative affect in healthy but sedentary adults. In the present study, we test the effects of a 3-month randomized controlled trial of aerobic exercise training in young to midlife adults on trait measures of depression, anxiety, hostility, and anger.

METHOD

One-hundred and 19 men (n = 56) and women (n = 63) aged 20-45 were randomized to 1 of 2 conditions: (a) 12 weeks of aerobic exercise after which they were asked to halt exercising and decondition for 4 weeks, or (b) a 16-week waitlist control group. Assessments of depression, anxiety, hostility and anger were completed at study entry, Week 12 and Week 16.

RESULTS

At study entry, participants scored low on measures of depression, anxiety, hostility and anger. Analyses among the intent-to-treat and per protocol samples found significant treatment effects of aerobic training for hostility and depression, but not for anxiety and anger. Within-group analyses demonstrated that depression and hostility scores decreased in the exercise group over the course of the intervention, while remaining stable in the control group. These effects persisted for the exercise group at nonsignificant levels after 4 weeks of deconditioning.

CONCLUSIONS

Aerobic exercise training has significant psychological effects even in sedentary yet euthymic adults, adding experimental data on the known benefits of exercise in this population. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Functionality and Neurocognition in Patients With Bipolar Disorder After a Physical-Exercise Program (FINEXT-BD Study): Protocol of a Randomized Interventionist Program

Introduction: Recent studies have shown that symptoms of psychiatric illness, functionality, and cognitive function improve with exercise. The aim of this study will be to investigate whether the implementation of an individualized exercise program will improve the functional status of patients with bipolar disorder (BD). Methods: This longitudinal, interventional, randomized, controlled, simple-blind clinical trial will include 80 patients aged 18-65 years, all of them with BD diagnosis. Patients will be randomly assigned to a physical exercise intervention + Treatment-As-Usual (TAU) group and a non-intervention + TAU group. Patients will be assessed by an extensive battery of clinical tests, physical parameters (e.g., brain structure changes measured by optical coherence tomography, cardiorespiratory fitness) and biological parameters (inflammation, oxidative stress and neurotrophic factors) at baseline, after a 4-month intervention period, and 6-month follow-up. Discussion: This is an innovative study aimed at gaining a deeper understanding of the physiopathology of BD and determining whether the prognosis and evolution of the disease can be improved through modifiable areas of the patient's lifestyle. Clinical Trial Registration: NCT04400630. NCT clinicaltrials.gov. Date of registration in primary registry 22 May 2020. clinicaltrials.gov.

Behavioural activation therapy to improve participation in adults with depression following brain injury: A single-case experimental design study

Following brain injury, the risk of depression increases. There are few studies of non-pharmacological interventions for this problem. Behavioural Activation (BA) could help because it has been demonstrated to be as effective as cognitive-behaviour therapy but is less cognitively demanding and more suitable for people with brain impairment. The current study evaluated BA using a multiple-baseline design across behaviours with replication. Three male participants with clinically significant depressive symptoms (two with traumatic brain injury aged 26 and 46, one who experienced strokes in infancy, aged 26) engaged in a 10-14-week trial of BA focusing on three activity domains: physical, social and functional activities. Participants completed an online form three times a day which recorded activity participation and responses to a single-item mood scale. There was little evidence in support of BA for increasing participation. There was also a lack of change in average mood, but some positive effects were found on measures of depression symptoms and quality of life in these participants. Various factors affected participation which might have been mitigated by extended treatment contact, greater use of prompts or electronic aids or the addition of other therapy modes.

Genomics and psychological resilience: a research agenda

Although exposure to adversity increases risk for poor mental health outcomes, many people exposed to adversity do not develop such outcomes. Psychological resilience, defined broadly as positive emotional and/or behavioral adaptation to adversity, may be influenced by genetic factors that have remained largely unexplored in the era of large-scale genome-wide studies. In this perspective, we provide an integrative framework for studying human genome-wide variation underlying resilience. We first outline three complementary working definitions of psychological resilience-as a capacity, process, and outcome. For each definition, we review emerging empirical evidence, including findings from positive psychology, to illustrate how a resilience-based framework can guide novel and fruitful directions for the field of psychiatric genomics, distinct from the ongoing study of psychiatric risk and related traits. Finally, we provide practical recommendations for future genomic research on resilience, highlighting a need to augment cross-sectional findings with prospective designs that include detailed measurement of adversities and outcomes. A research framework that explicitly addresses resilience could help us to probe biological mechanisms of stress adaptation, identify individuals who may benefit the most from prevention and early intervention, and ascertain modifiable protective factors that mitigate negative outcomes even for those at high genetic risk.

Physical activity of people with mental disorders compared to the general population: a systematic review of longitudinal cohort studies

PURPOSE

We investigated if (a) people with lower physical activity have an increased risk of subsequent mental disorders (compared to those with higher physical activity); and (b) people with mental disorders have reduced subsequent physical activity (compared to those without mental disorders).

METHODS

A systematic review of population-based longitudinal studies examining physical activity and mental disorders was conducted. Mental disorders were defined by International Classification of Diseases or Diagnostic and Statistical Manual of Mental Disorders. The results were described in a narrative summary.

RESULTS

Twenty-two studies were included. The majority (19) examined mood disorders and physical activity. Only two studies found consistent association between lower physical activity and a reduced risk of subsequent mental disorders. One study found the bidirectional association between physical activity and major depression. Twelve studies found mixed results (i.e., no consistency in direction and significance of the findings), and seven studies found no association between the variables of interest.

CONCLUSIONS

There is a lack of consistent evidence linking physical activity to be either a risk factor or consequence of mental disorders.

PROSPERO REGISTRATION ID

CRD42017071737.

Economic value of protected areas via visitor mental health

We evaluate methods to calculate the economic value of protected areas derived from the improved mental health of visitors. A conservative global estimate using quality-adjusted life years, a standard measure in health economics, is US$6 trillion p.a. This is an order of magnitude greater than the global value of protected area tourism, and two to three orders greater than global aggregate protected area management agency budgets. Future research should: refine this estimate using more precise methods; consider interactions between health and conservation policies and budgets at national scales; and examine links between personalities and protected area experiences at individual scale.

Long distance ski racing is associated with lower long-term incidence of depression in a population based, large-scale study

Physical activity has been proposed to be beneficial for prevention of depression, although the importance of exercise intensity, sex-specific mechanisms, and duration of the effects need to be clarified. Using an observational study design, following 395,369 individuals up to 21 years we studied whether participation in an ultralong-distance cross-country ski race was associated with lower risk of developing depression. Skiers (participants in the race) and matched non-skiers from the general population (non-participants in the race) were studied after participation (same year for non-participation) in the race using the Swedish population and patient registries. The risk of depression in skiers (n = 197,685, median age 36 years, 38% women) was significantly lower, to nearly half of that in non-skiers (adjusted hazard ratio, HR 0.53) over the follow-up period. Further, a higher fitness level (measured as the finishing time to complete the race, a proxy for higher exercise dose) was associated with lower incidence of depression in men (adjusted HR 0.65), but not in women. Our results support the recommendations of engaging in physical activity as a preventive strategy decreasing the risk for depression in both men and women. Furthermore, the exercise could reduce risk for depression in a dose-dependent matter, in particular in males.

Physical Activity and the Risk of Liver Cancer: A Systematic Review and Meta-Analysis of Prospective Studies and a Bias Analysis

BACKGROUND

Physical inactivity is an established risk factor for several cancers of the digestive system and female reproductive organs, but the evidence for liver cancers is less conclusive.

METHODS

The aim of this study was to synthesize prospective observational studies on the association of physical activity and liver cancer risk by means of a systematic review and meta-analysis. We searched Medline, Embase, and Scopus from inception to January 2019 for prospective studies investigating the association of physical activity and liver cancer risk. We calculated mean hazard ratios (HRs) and 95% confidence intervals (CIs) using a random-effects model. We quantified the extent to which an unmeasured confounder or an unaccounted selection variable could shift the mean hazard ratio to the null.

RESULTS

Fourteen prospective studies, including 6,440 liver cancers, were included in the systematic review and meta-analysis. The mean hazard ratio for high compared with low physical activity was 0.75 (95% CI = 0.63 to 0.89; 95% prediction interval = 0.52 to 1.07; I² = 64.2%). We estimated that 67.6% (95% CI = 56.6% to 78.5%) of all true effect estimates would have a hazard ratio less than 0.8. Bias analysis suggested than an unobserved confounder would have to be associated with a 1.99-fold increase in the risk of physical activity or liver cancer to explain away the observed mean hazard ratio. An unaccounted for selection variable would have to be related to exposure and endpoint with a relative risk of 1.58 to explain away the mean hazard ratio.

CONCLUSIONS

Physical activity is inversely related to the risk of liver cancer. Further studies with objectively measured physical activity and quasi-experimental designs addressing confounding are needed.

Development of the Impact of Physical Activity Scale

Despite evidence that exercise has physical and mental benefits, there is still a high dropout rate. One reason for why people struggle to maintain consistency in their workout programs is self-efficacy, the cognitive mechanism that predicts behavioral intention. Given that emotional arousal plays an important role in self-efficacy, we developed the Impact of Physical Activity (IPA) scale to investigate how positive and negative affect influence commitment to exercise. The findings demonstrate good internal reliability of the scale, as well as convergent and divergent validity with optimism and depression. The IPA also had good predictive validity of physical self-efficacy.

Physical activity and sedentary levels among people living with epilepsy: A systematic review and meta-analysis

How physically active and sedentary people with epilepsy are is unclear. We conducted a meta-analysis to investigate physical activity and sedentary behavior levels compared with the general population in people with epilepsy across the lifespan. Embase, PubMed, PsycARTICLES, and CINAHL Plus were searched from inception until 1/3/2019. A random effects meta-analysis was conducted. Adults with epilepsy (mean age range = 30-47 years) were significantly less likely to comply with physical activity recommendations [odds ratio (OR) = 0.68; 95% confidence interval (CI) = 0.53-0.87; P < 0.001; N analyses = 10; n epilepsy = 1599; n controls = 137,800] and more likely to be inactive (as defined by individual study criteria) (OR = 1.57; 95% CI = 1.34-1.84; P < 0.001; N analyses = 6; n epilepsy = 6032; n controls = 928,184). Data in children (mean age range = 10-12 years) were limited (N = 4; n = 170) and inconsistent while there were no data available for middle-aged and old age (>65 years) people with epilepsy. Our data demonstrate that adults with epilepsy are less physically active than the general population. Public health campaigns specifically targeting the prevention of physical inactivity in adults with epilepsy are warranted. More research on physical activity and sedentary levels in children, adolescents, middle-aged, and old age but also adult people with epilepsy is needed before specific recommendations can be formulated.

Objectively measured physical activity and depressive symptoms in adult outpatients diagnosed with major depression. Clinical perspectives

Physical activity (PA) is linked to reduced risk of depression, but research on the objectively measured PA in clinically diagnosed adult outpatients with major depressive disorder (MDD) is scarce. This study aimed to examine relationships of objectively measured PA with depression and mood. A total of 19 outpatients (6 males) with MDD, a mean age of 47.79 ± 11.67 years and mild-moderate depression participated in the study. To record PA, participants wore a triaxial accelerometer device on the right hip during waking hours for seven consecutive days. Depression and mood were assessed with self-reports immediately after day seven. Participants wore the accelerometers for a high number of days (M = 6.26 ± 1.24 days) and hours per day (13.40 ± 2.61 h), recording light (266.01 ± 100.74 min/day) or moderate (31.19 ± 24.90 min/day) PA, and sedentary time (515.33 ± 155.71 min/day). Stepwise regression analysis yield a significant prediction (p < .05) with only moderate PA contributing to the prediction of depression (Beta = -0.47, p < .05). The model explained 22% of the variance of depression. Our findings provide valuable preliminary evidence regarding the relationship between objectively measured PA and lower depression in clinically diagnosed outpatients with MDD, suggesting moderate PA may help alleviating depressive symptoms.

Digital Phenotyping With Mobile and Wearable Devices: Advanced Symptom Measurement in Child and Adolescent Depression

With an estimated 75% of all mental disorders beginning in the first two decades of life,¹ childhood and adolescence are crucial developmental periods to identify and intercept the unfolding of mental health problems, their relationships with physical health, and the multiple, interwoven connections to the surrounding environment.² Because an individual's mental health is best conceptualized, captured, and treated by taking into account the network of physiological and social functions that constitute the context of individual experience, accessing and analyzing data on multiple health indicators simultaneously can accelerate prediction of disease progression. With the advent of new technologies, dense and extensive amounts of biopsychosocial readouts that can be translated into clinically relevant information have become available in real time, with the potential to revolutionize the practice of medicine. However, challenges to this more ecological and comprehensive approach to mental health measurement include the actual capacity of capturing, safely storing, and analyzing dense data sets (encompassing, for example, mood, cognitions, physical activity, sleep, social interactions) from multiple synchronized sources, and identifying which among multiple indicators ultimately prove useful to improve prediction of a deterioration in symptoms and of initiating early intervention. In this Translations article, we focus on digital phenotyping (DP), which relates to the capturing of the aforementioned relevant biopsychosocial data. This concept is rapidly growing and gaining relevance to child and adolescent psychiatry, and is connected with overarching data science themes of "big data" (extremely large data sets, including data from electronic medical records, imaging, genomics, and patients' smartphones),^3,4 in addition to "machine learning" (the science of getting computers to act without being explicitly programmed)⁵ and "precision medicine" (the practice of custom tailoring treatments to a patient's disease processes),⁶ which have all received attention in this journal. We will describe principles and current applications of DP, together with its potential to facilitate improved outcomes and its limits, using depression in children and adolescents as an illustrative example.

Major depression and small vessel stroke: a Mendelian randomization analysis

BACKGROUND AND PURPOSE

Although observational studies have reported a positive association between depression and ischemic stroke, causality remains inconclusive. We aimed to assess the causal relationship of major depressive disorder (MDD) with ischemic stroke, especially with the small vessel stroke (SVS) subtype.

METHODS

We used 72 independent single-nucleotide polymorphisms associated with MDD in a genome-wide association study (GWAS) from the Psychiatric Genetics Consortium as instrumental variables. The corresponding data for ischemic stroke and its subtypes of European ancestry were available from the MEGASTROKE consortium of 34,217 ischemic stroke cases and 406,111 controls. Primary Mendelian randomization estimates were calculated with inverse-variance weighted method, and several alternate methods and multiple sensitivity analyses were also performed.

RESULTS

We found that genetic predisposition to higher risk of MDD was associated with higher risk of SVS, with an odds ratio of 1.33 (95% confidence interval, 1.08-1.65; p = 0.009) per log-odds increment in MDD risk, but not with large artery stroke (OR, 1.08; 95% CI 0.83-1.41; p = 0.559), cardioembolic stroke (OR, 0.98; 95% CI 0.80-1.20; p = 0.833), or all ischemic stroke (OR, 1.03; 95% CI 0.92-1.15; p = 0.633). The association of MDD with SVS was overall robust to sensitivity analyses.

CONCLUSIONS

We provided evidence for a possible causal effect of MDD on increased risk of SVS. Future researches are required to investigate whether rational intervention on depression may help to reduce societal burden of SVS.

Predicting Polygenic Risk of Psychiatric Disorders

Genetics provides two major opportunities for understanding human disease-as a transformative line of etiological inquiry and as a biomarker for heritable diseases. In psychiatry, biomarkers are very much needed for both research and treatment, given the heterogenous populations identified by current phenomenologically based diagnostic systems. To date, however, useful and valid biomarkers have been scant owing to the inaccessibility and complexity of human brain tissue and consequent lack of insight into disease mechanisms. Genetic biomarkers are therefore especially promising for psychiatric disorders. Genome-wide association studies of common diseases have matured over the last decade, generating the knowledge base for increasingly informative individual-level genetic risk prediction. In this review, we discuss fundamental concepts involved in computing genetic risk with current methods, strengths and weaknesses of various approaches, assessments of utility, and applications to various psychiatric disorders and related traits. Although genetic risk prediction has become increasingly straightforward to apply and common in published studies, there are important pitfalls to avoid. At present, the clinical utility of genetic risk prediction is still low; however, there is significant promise for future clinical applications as the ancestral diversity and sample sizes of genome-wide association studies increase. We discuss emerging data and methods aimed at improving the value of genetic risk prediction for disentangling disease mechanisms and stratifying subjects for epidemiological and clinical studies. For all applications, it is absolutely critical that polygenic risk prediction is applied with appropriate methodology and control for confounding to avoid repeating some mistakes of the candidate gene era.

Genetic influences on treatment-seeking for common mental health problems in the UK biobank

The majority of those who experience clinical anxiety and/or depressive symptoms in the population do not receive treatment. Studies investigating inequalities in treatment outcomes rarely consider that individuals respond differently to their experience of the environment. Much of our environment is under genetic influence, via our behaviour, whereby individuals actively select their experiences. If genes influence who seeks and receives treatment, selection bias will confound genomic studies of treatment response. Furthermore, if some individuals are at high genetic risk of needing but not commencing treatment, then greater efforts could be made to engage them. The role of common genetic variation on four lifetime treatment-seeking behaviours (treatment-seeking, treatment-receipt, self-help, self-medication with alcohol/drugs) was examined in participants of the UK Biobank (sample size range: 48,106 - 75,322). Treatment-related behaviours were only modestly heritable in these data. Nonetheless, genetic correlations reveal substantial genetic overlap between lifetime treatment-related behaviours and psychiatric disorders, symptoms and behavioural traits. To our knowledge, this is the first study to examine genetic influences on treatment-related behaviours. Further work is required to determine whether genetic factors could be used alongside clinical, social and demographic factors to identify at risk groups and inform strategies which target early intervention.

Association of Economic Status and Educational Attainment With Posttraumatic Stress Disorder: A Mendelian Randomization Study

Importance

There is a well-established negative association of educational attainment (EA) and other traits related to cognitive ability with posttraumatic stress disorder (PTSD), but the underlying mechanisms are poorly understood.

Objectives

To investigate the association of PTSD with traits related to EA.

Design, Setting, and Participants

Genetic correlation, polygenic risk scoring, and mendelian randomization (MR) were conducted including 23 185 individuals with PTSD and 151 309 control participants from the Psychiatric Genomics Consortium for PTSD and up to 1 131 881 individuals assessed for EA and related traits from UK Biobank, 23andMe, and the Social Science Genetic Association Consortium. Data were analyzed from July 3 through November 19, 2018.

Main Outcomes and Measures

Genetic correlation obtained from linkage disequilibrium score regression, phenotypic variance explained by polygenic risk scores, and association estimates from MR.

Results

Summary association data from multiple genome-wide association studies were available for a total of 1 180 352 participants (634 391 [53.7%] women). Posttraumatic stress disorder showed negative genetic correlations with EA (rg = -0.26; SE = 0.05; P = 4.60 × 10-8). Mendelian randomization analysis, conducting considering a random-effects inverse-variance weighted method, indicated that EA has a negative association with PTSD (β = -0.23; 95% CI, -0.07 to -0.39; P = .004). Investigating potential mediators of the EA-PTSD association, propensity for trauma exposure and risk-taking behaviors were observed as risk factors for PTSD independent of EA (trauma exposure: β = 0.37; 95% CI, 0.19 to 0.52; P = 2.57 × 10-5; risk-taking: β = 0.76; 95% CI, 0.38 to 1.13; P = 1.13 × 10-4), while income may mediate the association of EA with PSTD (MR income: β = -0.18; 95% CI, -0.29 to -0.07; P = .001; MR EA: β = -0.23; 95% CI, -0.39 to -0.07; P = .004; multivariable MR income: β = -0.32; 95% CI, -0.57 to 0.07; P = .02; multivariable MR EA: β = -0.04; 95% CI, -0.29 to 0.21; SE, 0.13; P = .79).

Conclusions and Relevance

Large-scale genomic data sets add further evidence to the negative association of EA with PTSD, also supporting the role of economic status as a mediator in the association observed.