Natural environments and craving: The mediating role of negative affect
Introduction
Smoking, drinking excessive amounts of alcohol, unhealthy eating and illicit drug use pose some of the greatest challenges to public health (Beaglehole et al., 2011; Sturm, 2002). In many cases an immediate precursor of these behaviours is an emotionally charged mental state characterised by an intense desire to engage in the behaviour, frequently referred to as a craving (May et al., 2015). As well as predicting consumption patterns across a range of unhealthy behaviours (Smoking, Cosci, Bertoli, Pistelli & Carrozzi, 2016; Snacking, Richard, Meule, Reichenberger & Blechert, 2017; Hamilton et al., 2013; Binge-drinking, Rosenberg and Mazzola, 2007), craving also predicts relapse rates for abstinent smokers (Berlin et al., 2013), alcohol-dependent individuals (Bottlender and Soyka, 2004), and dieters (Sitton, 1991). Both the strength and frequency of cravings are predicted by negative affective states such as stress, anxiety and depression (Kavanagh et al., 2009; McCaul et al., 2017). In other words, people are most likely to experience more frequent and intense cravings, and act on these cravings, when they are in negative affective states.
Consequently, there have been various attempts to reduce cravings and their associated negative consumption behaviours though reducing negative affect, notably through encouraging bouts of light-moderate physical activity (Haasova et al., 2013; Taylor et al., 2007; Ussher et al., 2012). There is good evidence that physical activity in and of itself can improve mood (Fox, 1999). However, much of the previous research into physical activity and craving in particular involved physical activity, such as walking and cycling outside and in quasi-natural environments such as parks (Haasova et al., 2013). This is potentially important because there is also evidence that physical activity undertaken in natural settings is associated with weaker negative emotions than activity conducted indoors or in built-up and urban settings (Thompson Coon et al., 2011). In other words, it is unclear if reductions in cravings in earlier studies was due to the physical activity itself or to the environment where it took place.
There is now a considerable body of evidence showing that even short (e.g. 10–15 minute) exposures to natural environments are associated with a reduction in negative (e.g. anxiety) affective states (Bowler et al., 2010; McMahan and Estes, 2015). Moreover, the more frequently an individual makes recreational visits to natural environments, the lower their odds of exhibiting mild-to-moderate depression (Cox et al., 2017), and the greater their odds of reporting high levels of eudaimonic well-being (i.e. the feeling that one's life is worthwhile; White et al., 2017).
Chronic exposure to natural environments, in the form of higher levels of neighbourhood greenspace, is also associated with reduced stress (Ward-Thompson et al., 2016), depression and negative affect (Beyer et al., 2014; Cox et al., 2017), even among identical twins (Cohen-Cline et al., 2015). Similar affective benefits are observed for green residential views and access to gardens/allotments (Kaplan, 2001; Ward-Thompson et al., 2016). In short, given the relationship between affect and craving, it seems plausible to hypothesise that individuals with greater exposure to natural environments will also have lower frequency and intensity of cravings because they have generally lower levels of negative affect. Two further strands of evidence support this possibility.
First, at least two nature-based treatment programmes have shown attenuated cravings amongst individuals undergoing drug and alcohol rehabilitation. Bennett et al. (1998) compared the efficacy of a three-day wilderness experience and treatment-as-usual within a residential setting. They found that post-intervention craving scores were lower in participants assigned to the intervention, relative to those who received residential treatment. Further, in a qualitative study, White et al. (2016) reported improvements in affect and reductions in craving in individuals undergoing drug and alcohol rehabilitation, following a week-long sail training voyage.
The second strand of evidence is incidental. Specifically, we know of several studies which have used an imagery based task to help reduce craving, where the imagery involved a natural setting (e.g. beach, Versland and Rosenberg, 2007; woodland, Hamilton et al., 2013). Thus, similar to the physical activity studies reviewed above, it remains possible that it was imagery of nature, rather than images per se, that were responsible for the reduction in cravings.
Given the potential for natural environments to offer a cost-effective and unobtrusive means of reducing craving, it is important to establish not only the mechanisms which may underlie this relationship, but also which particular components of nature exposure are the most likely candidates for reducing craving. The current study aimed to investigate these two underexplored issues, using a cross-sectional approach to explore our conceptual model. Specifically, an online survey across Southern England was utilised to provide an initial test of the associations between various types of nature exposure, craving and negative affect. Briefly, the strength and frequency of cravings were assessed using the Craving Experiences Questionnaire (May et al., 2014), and the Depression, Anxiety and Stress Scale (Lovibond and Lovibond, 1995) constituted a measure of negative affect. Consistent with prior research, local nature exposure was operationalised in terms of: 1) the proportion of greenspace in an individual's residential neighbourhood; the presence of green views from their home; their access to a garden/allotment; and 4) their frequency of use of public greenspaces.
The study addressed two principal research questions: 1) Is greater exposure to natural environments associated with reduced craving? and 2) Is any such relationship mediated by negative affect? In addition, the relative contributions of different types of nature exposure on craving and affect were investigated. Hypothesised relationships are depicted in Fig. 1. Based on prior research on the general benefits of nature, inverse relationships were predicted between exposure to natural environments and both the strength and frequency of craving. Additionally, it was hypothesised that these relationships would be mediated by reductions in negative affect. In line with prior research on the broader psychological benefits of nature (White et al., 2013), the contributions of different types of nature exposures were expected to be cumulative.
Section snippets
Participants
A cross-sectional online survey was designed and sent to two occupational cohorts: 1) Employees of Health Education England and NHS partnership organisations across Southern England and 2) Employees at the University of Plymouth. The final sample comprised of a total 149 participants (112 females) aged between 21 and 65 years (median age = 41 years).
Measures
The face validity of the survey was examined through a small-scale pilot study administered to an opportunity sample (N = 6) to ensure that the
Statistical approach
Analyses were conducted using STATA 14 (StataCorp, College Station, TX). T-tests were conducted to examine the bivariate effects of each environmental indicator (neighbourhood greenspace, view, garden, visit frequency) on the two main outcome variables (craving strength and frequency) predicted mediator (negative affect).
A series of multiple regression models were then fitted to examine the relative contribution of environmental indicators to each outcome measure, as well as the hypothesised
Discussion
To our knowledge, this study constitutes the first quantitative investigation of the associations between exposure to natural environments, craving for a range of appetitive substances and affect. The aims of the study were threefold: 1) to establish whether increased exposure to natural environments was associated with reduced craving; 2) to assess which types of nature exposure were most relevant to craving, and 3) to examine whether reductions in negative affect underlie the relationships
Conflicts of interest
None.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Acknowledgements:
This study was conducted as part of the first author's MSc in Psychological Research Methods and supervised by the second author.
References (63)
- et al.
Priority actions for the non-communicable disease crisis
The Lancet
(2011) - et al.
Effects of a therapeutic camping program on addiction recovery: the Algonquin Haymarket relapse prevention program
J. Subst. Abus. Treat.
(1998) - et al.
Predicting smoking relapse with a multidimensional versus a single-item tobacco craving measure
Drug Alcohol Depend.
(2013) - et al.
The benefits of nature experience: improved affect and cognition
Landsc. Urban Plan.
(2015) - et al.
The effect of rumination on craving across the continuum of drinking behaviour
Addict. Behav.
(2013) - et al.
Evaluating the relative influence on population health of domestic gardens and green space along a rural-urban gradient
Landsc. Urban Plan.
(2017) - et al.
Tracking human activity and well-being in natural environments using wearable sensors and experience sampling
Soc. Sci. Med.
(2014) - et al.
Brief guided imagery and body scanning interventions reduce food cravings
Appetite
(2013) The restorative benefits of nature: toward an integrative framework
J. Environ. Psychol.
(1995)- et al.
The structure of negative emotional states:comparison of the depression anxiety stress scales (DASS) with the beck depression and anxiety inventories
Behav. Res. Ther.
(1995)
The elaborated intrusion theory of desire: a 10-year retrospective and implications for addiction treatments
Addict. Behav.
Poor response inhibition as a predictor of problem drinking and illicit drug use in adolescents at risk for alcoholism and other substance use disorders
J. Am. Acad. Child Adolesc. Psychiatry
Food cravings in everyday life: an EMA study on snack-related thoughts, cravings, and consumption
Appetite
Relationships among self-report assessments of craving in binge-drinking university students
Addict. Behav.
Socio-economic inequalities in access to nature on public and private lands: a case study from Brisbane, Australia
Landsc. Urban Plan.
Playing Tetris decreases drug and other cravings in real world settings
Addict. Behav.
Socioeconomic status and the 25× 25 risk factors as determinants of premature mortality: a multicohort study and meta-analysis of 1· 7 million men and women
The Lancet
Natural outdoor environments and mental and physical health: relationships and mechanisms
Environ. Int.
Coastal proximity, health and well-being: results from a longitudinal panel survey
Health Place
Recreational physical activity in natural environments and implications for health: a population based cross-sectional study in England
Prev. Med.
Natural environments and subjective wellbeing: different types of exposure are associated with different aspects of wellbeing
Health Place
The association between green space and mental health varies across the lifecourse. A longitudinal study
J. Epidemiol. Community Health
The moderator–mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations
J. Personal. Soc. Psychol.
Exposure to neighbourhood green space and mental health: evidence from the survey of the health of Wisconsin
Int. J. Environ. Res. Public Health
Parks and people: an environmental justice inquiry in Baltimore, Maryland
Ann. Assoc. Am. Geogr.
Impact of craving on alcohol relapse during, and 12 months following, outpatient treatment
Alcohol Alcohol
A systematic review of evidence for the added benefits to health of exposure to natural environments
BMC Public Health
Physical Activity Guidelines in the U.K: Review and Recommendations. School of Sport, Exercise and Health Sciences
Access to green space, physical activity and mental health: a twin study
J. Epidemiol. Community Health
Depressive, anxious, withdrawal symptoms, and craving as possible predictors of abstinence maintenance in smokers attending a 12-week quitting program
Med. Express
Doses of nearby nature simultaneously associated with multiple health benefits
Int. J. Environ. Res. Public Health
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2023, New Ideas in PsychologyCitation Excerpt :Finally, recent research has suggested that environmental variables are potentially relevant for preventing substance use and mental health issues. Indeed, cumulative evidence links environmental and social variables such as neighbourhood socioeconomic status (Karriker-Jaffe, 2013), presence of green spaces (Martin et al., 2019; Wiley et al., 2020), density of betting venues (Badji et al., 2020), among others, to severity of addiction. Fig. 1 shows a graphical representation of the proposed model.
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2022, Journal of Environmental PsychologyCitation Excerpt :Furthermore, we studied craving measures that address the assumed differing energy demands for processing nature and urban images, as was suggested by the PFA and other researchers (cf. Grassini et al., 2019; Joye & van den Berg, 2011). As nature exposure was associated with reduced craving in previous studies (Martin et al., 2019; Wu & Chiou, 2019), we assumed lower food craving after nature compared to urban image exposure. Since we were primarily interested in the nature-urban comparison within each image type, a-priori sample size determination was calculated for an ANOVA with a two-level between-subjects factor (nature, urban) and two within-subject measurements (pre, post) using α = 0.05, power = .80, and f = 0.25.