02_litreview.qmd

# Literature Review

In the United States, the prevalence of mental illnesses among adults, aged 18 or older, rose from 19.1% in 2018 to 22.8% in 2021 [@mackettMentalHealthTravel2021; @MentalHealthNumbers2023]. Mental health and well-being are influenced by various factors, including social and environmental elements as well as travel behavior [@barryAddressingDeterminantsPositive2009; @delboscExploringRelativeInfluences2011].

Social isolation and loneliness are critical determinants of mental health, with substantial evidence linking them to increased rates of anxiety, depression, and other mental health disorders [@loadesRapidSystematicReview2020. The ability to travel and engage with others plays a vital role in mitigating these feelings. During significant periods of isolation, such as the COVID-19 lockdowns, the lack of social interactions highlighted the importance of mobility in maintaining mental well-being. Studies have indicated that social support networks and access to transportation are essential for fostering connections and enhancing overall mental health [@stanleyMobilitySocialExclusion2011; @delboscExploringRelativeInfluences2011].

The relationship between the built and natural environments and mental health is multifaceted, with various activity locations playing roles in influencing well-being. Green and blue spaces, for instance, have been shown to alleviate stress, anxiety, and depression, enhancing mood and bolstering cognitive function thus making them vital for enhancing mental health and overall well-being [@pousoContactBluegreenSpaces2021; @whiteAssociationsGreenBlue2021; @pelgrimsAssociationUrbanEnvironment2021; @rautioLivingEnvironmentIts2018]. Similarly, libraries serve as essential community resources that not only provide access to information and educational materials but also foster a comforting atmosphere and therapeutic landscape that is welcoming, calming, empowering, and overall conducive to well-being [@eliaPublicLibrariesSupporting2019; @brewsterPublicLibraryTherapeutic2014].

On the other hand, grocery stores and social recreation spaces, such as restaurants and theaters, present a more complex picture. Grocery shopping can induce stress due to factors like time pressure and crowd density, which can negatively impact shopping satisfaction as well as overall mental well-being [@aylottExploratoryStudyGrocery1998; @nilssonEffectsTimePressure2017]. In contrast, social recreation spaces offer opportunities for socialization and relaxation, which can enhance well-being by eliciting positive emotions and fostering long-term stress-coping mechanisms [@takiguchiRelationshipLeisureActivities2022] Researchers found a positive link between leisure satisfaction and well-being over time @kuykendallLeisureEngagementSubjective2015\]. However, the quality of social interactions in these environments is crucial; supportive interactions can lead to higher quality of life, while negative interactions can diminish well-being [@yanosNegativeSupportiveSocial2001].

Moreover, the impact of social deprivation and loneliness on mental health remains a challenge, as individuals may experience loneliness even in crowded environments [@orbenEffectsSocialDeprivation2020]. This highlights the intricate interaction between activities in built and natural environments and mental well-being, suggesting that visits to these locations can either bolster or hinder overall mental health, depending on the nature of the interactions experienced.

Research indicates a connection between travel behavior and mental well-being, with studies showing that travel satisfaction significantly impacts social and mental health. For instance, a study by @syahputriEffectTravelSatisfaction2022 found that individuals who reported higher travel satisfaction also experienced better mental health outcomes. However, while working or studying from home can enhance travel satisfaction, excessive time spent on obligatory activities may limit social interactions, negatively affecting mental health. Encouraging travel, even amidst significant commitments, can foster better social connections and mental well-being [@syahputriEffectTravelSatisfaction2022]. Additionally, regular commuters often report lower life satisfaction compared to those who work from home, yet general travel experiences are associated with improved mood and overall life satisfaction. These insights underscore the importance of integrating travel into daily routines as a strategy to enhance mental health and well-being, emphasizing that positive travel experiences can lead to significant improvements in emotional health and quality of life [@frimanHowDoesTravel2017].

Recent research by @lanDailySpacetimeActivities2022 used mobile phone-based sensing to explore the relationship between daily activities, environmental exposures, and anxiety symptoms. By tracking spatial movements through GPS and accelerometers, the study found that time spent in areas with high air pollution and noise was linked to increased anxiety, while exposure to green spaces correlated with lower anxiety levels. This research may have been been limited, however, by only including trips over a 7-day period. It also relied on a self-reported recollection of trips and trip location rather than an observation of where the trips or activities were located.

In spite of the numerous studies linking observed travel patterns to elements of mental health, numerous questions remain unanswered. Of particular importance are two that we hope to address in this research. First, existing studies often fail to control for preexisting or baseline mental health and its impacts on travel behavior; do people with neurotypologies or stressors predisposing them to heightened anxiety or depression **make fewer trips** than others, thus reversing the causality in the observed relationships? Second, regardless of neurotypology or mental health baseline, previous studies have failed to address the direction of causality in a compelling way. What is needed is a long-term observation of mental health indicators alongside travel and activity data on which baselines can be measured and the directionality evaluated.