***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Introduction Experimental studies have reported associations between short-term exposure to natural outdoor environments ( NOE ) and health benefits . However , they lack insight into mechanisms , often have low external and ecological validity , and have rarely focused on people with some psycho-physiological affection . The aim of this study was to use a r and omized , case-crossover design to investigate : ( i ) the effects of unconstrained exposure to real natural and urban environments on psycho-physiological indicators of people with indications of psychological distress , ( ii ) the possible differential effects of 30 and 30 + 180 minutes exposures , and ( iii ) the possible mechanisms explaining these effects . Material and methods People ( n = 26 ) with indications of psychological distress were exposed to green ( Collserola Natural Park ) , blue ( Castelldefels beach ) and urban ( Eixample neighbourhood ) environments in Catalonia .  They were exposed to all environments in groups for a period of 30 + 180 minutes between October 2013 and January 2014 . During the exposure period , participants were instructed to do what they would usually do in that environment . Before , during ( at 30 and 30 + 180 minutes ) and after each exposure , several psycho-physiological measures were taken : mood ( measured as Total Mood Disturbance , TMD ) , attention capacity ( measured as backwards digit-span task ) , stress levels ( measures as salivary cortisol ) , systolic and diastolic blood pressure , heart rate , autonomous nervous system ( assessed as heart rate variability and the indicators : low frequency power ( LF ) , high frequency power ( HF ) , ratio between LF and HF ( LF : HF ) , and coefficients of component variance of LF , HF , and LF : HF ) . We also measured several potential mediators : air pollution , noise , physical activity , social interactions , and self-perceived restoration experience . Results When compared with responses to urban environment , we found statistically significantly lower TMD [ -4.78 ( -7.77 , -1.79 ) points difference ] , and salivary cortisol [ -0.21 ( -0.34 , -0.08 ) log nmol/L ] in the green exposure environment , and statistically significantly lower TMD [ -4.53 ( -7.57 , -1.49 ) points difference ] , and statistically significant favourable changes in heart rate variability indicators ( specifically LF : HF and CCV-LF : HF with around -0.20 points of difference of the indicators ) in the blue exposure environment . Physical activity and self-perceived restoration experience partially mediated the associations between NOE and TMD . Physical activity and air pollution partially mediated the associations between NOE and heart rate variability . Discussion and conclusions This study extends the existing evidence on the benefits of NOE for people 's health . It also suggests NOE potential as a preventive medicine , specifically focusing on people with indications of psychological distress . Trial registration Clinical trials.gov In recent times , attention has been focused on the role of urban green spaces in promoting human health and well-being . However , there is a lack of evidence -based research on the physiological effects of walking in urban green areas . This study aim ed to clarify the physiological and psychological effects of walking in urban parks during fall . Twenty-three males ( mean age 22.3 ± 1.2 years ) were instructed to walk predetermined 15-min courses in an urban park and in a nearby city area ( control ) . Heart rate and heart rate variability were measured to assess physiological responses , and the semantic differential method , Profile of Mood States , and State-Trait Anxiety Inventory were used to measure psychological responses . We observed that walking in an urban park result ed in a significantly lower heart rate , higher parasympathetic nerve activity , and lower sympathetic nerve activity than walking through the city area . In subjective evaluations , participants were more “ comfortable , ” “ natural , ” “ relaxed , ” and “ vigorous ” after a walk in the urban park . Furthermore , they exhibited significantly lower levels of negative emotions and anxiety . These findings provide scientific evidence for the physiological and psychological relaxation effects of walking in urban parks during fall Developing an evidence base for making public health decisions will require using data from evaluation studies with r and omized and nonr and omized design s. Assessing individual studies and using studies in quantitative research syntheses require transparent reporting of the study , with sufficient detail and clarity to readily see differences and similarities among studies in the same area . The Consoli date d St and ards of Reporting Trials ( CONSORT ) statement provides guidelines for transparent reporting of r and omized clinical trials . We present the initial version of the Transparent Reporting of Evaluations with Nonr and omized Design s ( TREND ) statement . These guidelines emphasize the reporting of theories used and descriptions of intervention and comparison conditions , research design , and methods of adjusting for possible biases in evaluation studies that use nonr and omized design MOTIVATION Modern data acquisition based on high-throughput technology is often facing the problem of missing data . Algorithms commonly used in the analysis of such large-scale data often depend on a complete set . Missing value imputation offers a solution to this problem . However , the majority of available imputation methods are restricted to one type of variable only : continuous or categorical . For mixed-type data , the different types are usually h and led separately . Therefore , these methods ignore possible relations between variable types . We propose a non-parametric method which can cope with different types of variables simultaneously . RESULTS We compare several state of the art methods for the imputation of missing values . We propose and evaluate an iterative imputation method ( missForest ) based on a r and om forest . By averaging over many unpruned classification or regression trees , r and om forest intrinsically constitutes a multiple imputation scheme . Using the built-in out-of-bag error estimates of r and om forest , we are able to estimate the imputation error without the need of a test set . Evaluation is performed on multiple data sets coming from a diverse selection of biological fields with artificially introduced missing values ranging from 10 % to 30 % . We show that missForest can successfully h and le missing values , particularly in data sets including different types of variables . In our comparative study , missForest outperforms other methods of imputation especially in data setting s where complex interactions and non-linear relations are suspected . The out-of-bag imputation error estimates of missForest prove to be adequate in all setting s. Additionally , missForest exhibits attractive computational efficiency and can cope with high-dimensional data . AVAILABILITY The package missForest is freely available from http://stat.ethz.ch/CRAN/. CONTACT stekhoven@stat.math.ethz.ch ; The prevalence of depression may be affected by changes in psychiatric practice s and the availability of online mental health information in the past two decades . This study aim ed to evaluate the aggregate prevalence of  depression  in communities from different countries between 1994 and 2014 and to explore the variations in prevalence stratified by geographical , method ological and socio-economic factors . A total of 90 studies were identified and met the inclusion criteria ( n = 1,112,573 adults ) with 68 studies on single point prevalence , 9 studies on one-year prevalence , and 13 studies on lifetime prevalence of depression . A r and om-effects model meta- analysis that was performed to calculate the aggregate point , one-year and lifetime prevalence of depression calculated prevalences of 12.9 % , 7.2 % and 10.8 % respectively . Point prevalence of depression was significantly higher in women ( 14.4 % ) , countries with a medium human development index ( HDI ) ( 29.2 % ) , studies published from 2004 to 2014 ( 15.4 % ) and when using self-reporting instruments ( 17.3 % ) to assess depression . Heterogeneity was identified by meta-regression and subgroup analysis , and response rate , percentage of women and year of publication , respectively , were determined contribute to depression prevalence . This meta- analysis allows benchmarking of the prevalence of depression during the era when online health information emerged , facilitating future comparisons Introduction Exposure to nature may reduce stress in low-income parents . This prospect i ve r and omized trial compares the effect of a physician ’s counseling about nature with or without facilitated group outings on stress and other outcomes among low-income parents . Material s and methods Parents of patients aged 4–18 years at a clinic serving low-income families were r and omized to a supported park prescription versus independent park prescription  in a 2:1 ratio . Parents in both groups received physician counseling about nature , maps of local parks , a journal , and pedometer . The supported group received additional phone and text reminders to attend three weekly family nature outings with free transportation , food , and programming . Outcomes measured in parents at baseline , one month and three months post-enrollment included : stress ( using the 40-point Perceived Stress Scale [ PSS10 ] ) ; park visits per week ( self-report and journaling ) ; loneliness ( modified UCLA-Loneliness Scale ) ; physical activity ( self-report , journaling , pedometry ) ; physiologic stress ( salivary cortisol ) ; and nature affinity ( vali date d scale ) . Results We enrolled 78 parents , 50 in the supported and 28 in the independent group . One-month follow-up was available for 60 ( 77 % ) participants and three-month follow up for 65 ( 83 % ) . Overall stress decreased by 1.71 points ( 95 % CI , -3.15 , -0.26 ) . The improvement in stress did not differ significantly by group assignment , although the independent group had more park visits per week ( mean difference 1.75 ; 95 % CI [ 0.46 , 3.04 ] , p = 0.0085 ) . In multivariable analysis , each unit increase in park visits per week was associated with a significant and incremental decrease in stress ( change in PSS10–0.53 ; 95 % CI [ -0.89 , -0.16 ] ; p = 0.005 ) at three months . Conclusion While we were unable to demonstrate the additional benefit of group park visits , we observed an overall decrease in parental stress both overall and as a function of numbers of park visits per week . Paradoxically the park prescription without group park visits led to a greater increase in weekly park visits than the group visits . To underst and the benefits of this intervention , larger trials are needed . Trial registration Clinical Trials.gov OBJECTIVE To investigate the effects of short-term forest bathing on human health . METHODS Twenty healthy male university students participated as subjects and were r and omly divided into two groups of 10 . One group was sent on a two-night trip to a broad-leaved evergreen forest , and the other was sent to a city area . Serum cytokine levels reflecting inflammatory and stress response , indicators reflecting oxidative stress , the distribution of leukocyte subsets , and plasma endothelin-1 ( ET-1 ) concentrations were measured before and after the experiment to evaluate the positive health effects of forest environments . A profile of mood states ( POMS ) evaluation was used to assess changes in mood states . RESULTS No significant differences in the baseline values of the indicators were observed between the two groups before the experiment . Subjects exposed to the forest environment showed reduced oxidative stress and pro-inflammatory level , as evidence d by decreased malondialdehyde , interleukin-6 , and tumor necrosis factor a levels compared with the urban group . Serum cortisol levels were also lower than in the urban group . Notably , the concentration of plasma ET-1 was much lower in subjects exposed to the forest environment . The POMS evaluation showed that after exposure to the forest environment , subjects had lower scores in the negative subscales , and the score for vigor was increased . CONCLUSION Forest bathing is beneficial to human health , perhaps through preventive effects related to several pathological factors Aims : To assess the relationship between green space proximity , use of green space and depressive symptoms and perceived general health among a r and om sample men and women . Methods : Cross-sectional study of a population -based sample of 6,944 45–72 year old Kaunas city residents .  Self-reported question naires provided information on sociodemographic variables , health behaviours , depressive symptoms and poor and very poor perceived general health . Residential proximity to green spaces was defined as living less than 300 m , within interval of 300–999 m , and equal or more than 1 km from a park . The use of the park was divided into two categories : no park use or use < 4hrs/week and use of the park ≥4 h/week . The study received approval from the Kaunas Regional Research Ethics Committee . Multiple logistic regression assessed the associations controlling for confounding variables . Results : The prevalence of depressive symptoms and poor and or very poor perceived general health was higher in women than in men . The association between the use of the park and residential proximity to the park revealed that women living > 300 m from a green space and who used the space ≥4 h/week showed higher odds 1.92 ( 1.11–3.3 ) and 1.68 ( 0.81–3.48 ) of depressive symptoms and poor and very poor perceived general health as compared to those who used the park < 4 hrs/week and residential proximity was > 300 m. Conclusions : The results of our study confirmed an association between use of the green space , residential proximity , and depressive symptoms and poor and very poor perceived general health among women only Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more Non-r and omised studies of the effects of interventions are critical to many areas of healthcare evaluation , but their results may be biased . It is therefore important to underst and and appraise their strengths and weaknesses . We developed ROBINS-I ( “ Risk Of Bias In Non-r and omised Studies - of Intervent 
    Output:
    
A small effect was found for reduction in depressive mood following exposure to the natural environment .