Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, London
Section of Epidemiology, Institute of Psychiatry, London
Oxford Centre for Sustainable Development, School of Architecture, Oxford Brookes University, Oxford
National Centre for Social Research, London
Correspondence: Scott Weich, Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, UK. Tel: 020 7830 2350; fax: 020 7830 2802; e-mail: s.weich{at}rfc.ucl.ac.uk
Declaration of interest None. The study was funded by the Wellcome Trust.
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ABSTRACT |
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Aims The present study tested the hypothesis that the prevalence of depression is associated with independently rated measures of the built environment, after adjusting for individuals'socio-economic status and the internal characteristics of their dwellings.
Method Cross-sectional survey of 1887 individuals aged 16 years and over in two electoral wards in north London. Depression was ascertained using the Center for Epidemiologic Studies Depression scale (CESD). The built environment was rated independently, using a validated measure.
Results After adjusting for socio-economic status, floor of residence and structural housing problems, statistically significant associations were found between the prevalence of depression and living in housing areas characterised by properties with predominantly deck access (odds ratio=1.28, 95% CI 1.03-1.58; P=0.02) and of recent (post-1969) construction (odds ratio=1.43, 95% CI 1.06-1.91; P=0.02).
Conclusions The prevalence of depression was associated with independently rated features of the built environment, independent of individuals' socio-economic status and internal characteristics of dwellings.
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INTRODUCTION |
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METHOD |
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Individual respondents were selected in two stages using random probability sampling methods. The Postcode Address File (PAF) was used as the sampling frame for selecting about 1300 addresses within each ward. All addresses that were residential and occupied were eligible, and up to two adults (aged 16 years and over) were sampled at random within each household, without substitution, using a Kish grid technique (Kish, 1965).
Prevalence of depression
The prevalence of depression was assessed using the Center for
Epidemiologic Studies Depression scale (CESD;
Radloff, 1977; Roberts & Vernon, 1983;
Beekman et al, 1997),
which is a validated 20-item selfreport measure. Each item includes four
response categories, scored from 0 to 3. Those scoring 16 or more were
classified as cases (Frerichs
et al, 1981; Harlow
et al, 1999). Sensitivity analyses were conducted using
the CESD score as a continuous variable.
Socio-economic status and housing characteristics
Respondents were asked about their age, marital status, education,
ethnicity and employment status. Household-level risk factors for depression
included access to a car or van and the following characteristics of the
dwelling: tenure, level (floor on which entrance located) and the presence of
four structural problems (damp, leaking roof, rot in woodwork
and infestation). Respondents were asked how long they had lived in their
current dwelling.
Built environment site survey
Prior to the household survey, both wards were subdivided into discrete
housing areas by one of the authors (E.B.), who is a trained
architect/urban designer. A housing area was defined as a geographically
bounded area in which the majority of the housing was homogeneous in form and
character. Eighty-six housing areas were enumerated across the two wards.
The Built Environment Site Survey Checklist (BESSC)
The Built Environment Site Survey Checklist (BESSC) is a standardised,
validated inventory for rating housing areas, developed for this study
(Weich et al,
2001a). Items include the predominant form, height and
age of housing, number of dwellings and type of access, provision of gardens,
use of public space, amount of derelict land, security and distances to local
shops and amenities. The original version of the BESSC (available from authors
upon request) comprised 31 items, of which 25 had fixed categorical responses.
The remaining items required the researcher to rank features of the built
environment according to the proportion of space used in particular ways, and
to estimate the distance from the centre of the housing area to a range of
amenities. A postgraduate student in urban design carried out ratings,
independently of interviews with residents. Interrater reliability for BESSC
items was good, with 0.5 for 15 categorical items. The present
study was restricted to these items, as shown in
Table 2.
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Statistical analysis
Analyses were undertaken using survey commands within Stata
(Stata Corporation, 1999),
which adjusts standard errors and 2 statistics for clustering
(autocorrelation) within housing areas and households
(Huber, 1981). Data were
weighted by household size, to adjust point estimates for the probability of
selection. The outcome measure for our main analyses was caseness on the
CESD (score
16), as described above. Unadjusted and adjusted odds
ratios with 95% confidence intervals and likelihood ratio tests (LRTs) to
assess confounding were calculated using logistic regression. Sensitivity
analyses were carried out using linear (least-squares) regression for the
CESD score as a continuous measure. These analyses were undertaken to
evaluate associations between the CESD score and characteristics of the
built environment without the imposition of an arbitrary case threshold.
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RESULTS |
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Characteristics of the study sample are shown in Table 1. The prevalence of depression was higher to a statistically significant extent among women, those not married, individuals of non-White ethnicity, those without educational qualifications and those not in employment. Statistically significant associations with depression also were found for three out of four household-level risk factors, namely lack of access to a car or van, living in rented accommodation and living in a dwelling with structural problems (Table 1). No statistically significant associations were found between the duration that respondents had occupied their present dwelling and either the prevalence of depression or CESD score.
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Associations between the built environment and individual and
household-level risk factors
Statistically significant associations were found between characteristics
of the built environment and individuals' socio-economic status. Those living
in rented accommodation were significantly more likely to live in housing
areas with newer properties (2=18.8, P<0.0001),
dwellings with deck access (
2=7.7, P=0.007), few
private gardens (
2=15.5, P=0.002) and shared
recreational space (
2=23.9, P<0.0001), although
not more abundant graffiti (
2=1.8, P=0.18). Similar
patterns of associations with the built environment were found for
unemployment, lack of educational qualifications, non-White ethnicity and lack
of regular access to a car or van.
Statistically significant associations also were found between
characteristics of housing areas and those of respondents' dwellings.
Individuals who reported structural problems were likely to be living in
housing areas characterised by older (pre-1940) properties
(2=3.4, P=0.02). Those living in dwellings situated
above the ground floor were significantly more likely to be living in areas
with properties of more recent (1940 onwards) construction
(
2=2.6, P<0.05), with few private gardens
(
2=38.7, P<0.0001) and more shared recreational
spaces (
2=8.5, P=0.0006). Individuals in areas with
the oldest (i.e. pre-1940) dwellings were the least likely to live in areas
with predominantly deck access dwellings
(
2=4.49, P=0.04).
Respondents living in areas characterised by deck access homes
(2=3.91, P=0.03), graffiti (
2=3.93,
P=0.03) and without shared recreational spaces
(
2=5.41, P=0.01) reported living in their present
dwelling for longer than those in areas without these features.
Depression and the built environment
The prevalence of depression was higher to a statistically significant
degree in housing areas characterised by dwellings with deck access, abundant
graffiti, newer (1940 onwards) properties, public space(s) and few private
gardens (Table 2). After
further adjusting for individual and household-level risk factors for
depression (including floor of residence and structural housing problems),
statistically significant associations remained between the prevalence of
depression and living in housing areas characterised by dwellings with
predominantly deck access and those of most recent (post-1969) construction
(Table 3). The association with
the predominant age of properties in the housing area remained statistically
significant after adjusting for predominant type of access to dwellings.
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Associations with depressive symptoms, using CESD score as a
continuous measure, differed from those found for cases of
depression (CESD score 16) for three BESSC items (Tables
2 and
3). In contrast to findings for
cases of depression, no statistically significant associations were found
between CESD score and living in housing areas with predominantly deck
access dwellings or those in which fewer than one-quarter of dwellings had
private gardens (Table 2). By
contrast, a statistically significant association was found for living in a
housing area with at least one disused (derelict) building, although this
failed to reach statistical significance after adjusting for individual
socio-economic status (Table
3).
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DISCUSSION |
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Rating the built environment
An important strength of this study was the rating of the built environment
independently of the subjective judgements of local residents. Although
architects' judgements, particularly in terms of aesthetics, differ from those
of the general population (Devlin &
Nasar, 1989; Halpern,
1995) our aim was to evaluate associations between
objective measures of the built environment and the prevalence
of depression. Our built environment measure had the advantage of being
relatively simple and quick to administer, which was likely to have enhanced
its interrater reliability.
We were interested primarily in measuring the physical rather than the social environment. Although the latter may mediate the effects of the former, these should be measured independently. Although no operational definitions of incivilities exist, these are believed to comprise physical incivilities (derelict buildings, graffiti, litter, vandalism and excessive traffic, urine and faeces) (Coleman, 1985) and social incivilities (particularly teenage gangs and crime) (Halpern, 1995). The only direct objective measure of incivilities in this paper concerned graffiti. Our original built environment site survey measure (the BESSC) required raters to assess vandalism, but this item was dropped because of low interrater reliability (Weich et al, 2001a). Traffic, crime, teenage gangs and litter (and probably dog faeces) are more variable and harder to quantify reliably at this geographical level. Although crime may be an important risk factor for depression, the interrater reliability of observed criminal activity would probably be very low and would require longer periods of observation than were allowed for in this study. We therefore hypothesised that higher rates of depression would be found in areas where social incivilities (particularly crime) were most likely to occur, and that such areas would be characterised by derelict buildings and abundant graffiti, open public spaces and few buffers between public and private spaces.
Residents' definitions of the boundaries of their neighbourhood vary (Cohen et al, 2000) and there is no evidence concerning the area over which the effects of the built environment are likely to operate. By identifying areas of homogeneous housing type and form, the enumeration of housing areas was likely to have resulted in ratings of the built environment that were more reliable and valid than studies considering much larger geographical areas (Taylor et al, 1985). One important consequence of this approach was that the population size of housing areas varied considerably. Although this may have limited the power of some of the analyses (as a result of small cell sizes), we do not believe that this affected our main findings because all standard errors were adjusted for the clustering of respondents within housing areas.
Depressive symptoms and depressive episodes
The study was limited by use of the CESD rather than a standardised
clinical interview. Although the inner-city setting was likely to have
contributed to the high prevalence of depression, prevalence estimates are
generally larger in studies using self-report case-finding instruments
(Blazer et al, 1994; Meltzer et al, 1995).
Because the CESD enquires about experiences in the past week,
false positive cases might have included individuals with mild
or transient psychological disturbance. Nevertheless, even these less severe
forms of depression are of considerable public health importance. Depressive
symptoms are distributed continuously in the general population
(Meltzer et al, 1995)
and are associated in a linear fashion with social impairment, physical
morbidity and increased consultation rates in primary care.
Overall, the patterns of associations with the built environment were similar, irrespective of whether the outcome was treated as a continuous or dichotomous variable. However, for two BESSC items (deck access and proportion of homes with private gardens), statistically significant associations were found for cases of depression but not with (continuous) CESD score. Some features of the built environment, therefore, may be associated with moderate, rather than severe, depression. Finally, although use of the CESD may have overestimated the prevalence of cases of depression, this could not have accounted for our main finding, namely that the associations between depression and measures of the built environment were little affected by adjusting for individual socio-economic status.
Other limitations of this study
Although this was a cross-sectional study, our findings could not have been
due to recall bias on the part of respondents, because ratings of the built
environment were made independently of the ascertainment of depression.
Although reverse causality would seem improbable, social selection cannot be
ruled out. Individuals with a predisposition to depression may have been
placed selectively by the local authority in certain areas or in certain types
of property, although this was unlikely to have accounted for our findings.
Although those living in the least advantageous housing circumstances also
have the lowest socio-economic status, associations between the built
environment and depression were not explained by individual risk factors such
as unemployment. Nor can these findings be explained by sampling artefact.
Although there were a number of statistically significant differences between
the socio-economic and demographic characteristics of the residents of the two
wards, no such difference was found in the prevalence of depression or in the
characteristics of housing areas in which respondents lived. Furthermore, all
of the reported associations were adjusted for the clustering of respondents
within housing areas. Finally, duration of residence was not associated with
the prevalence of depression to a statistically significant degree. Those
living in the least advantageous areas (characterised, for example, by
graffiti and deck access dwellings) reported living in their homes for longer
than those living in better housing areas. Greater residential
stability in less desirable areas probably reflects a difficulty in moving,
because most individuals live in dwellings owned by the local authority and
housing transfers are rare. Although these considerations do not undermine the
validity of our findings, they can only truly be overcome by means of
longitudinal studies, of which there have been few
(Halpern, 1995;
Dalgard & Tambs, 1997). The
present findings represent the baseline phase of just such a study.
Another important consideration is selection bias arising from non-response. The household response rate was 61%, and 88% of eligible individuals in participating households were interviewed. These rates are similar to those found in other surveys in urban areas in the UK. However, selection bias may have affected the estimated prevalence of depression and estimates of exposure to the risk factors under study. For this to have significantly altered our estimates of associations between depression and characteristics of the built environment, non-participation would have to have been associated with both the prevalence of depression and the area of residence. For example, we would only have overestimated the associations of interest if non-respondents were more likely than respondents to have been depressed and living in housing areas characterised by homes of older (pre-1940) construction, with non-deck access, no graffiti and/or no shared recreational spaces.
The study was conducted in two electoral wards within one north London borough. Failure to find more statistically significant associations between the built environment and depression may have been due to the homogeneity of the built environment across the housing areas. These findings may not be generalisable elsewhere and require replication.
Depression and the built environment
The built environment cannot be equated with the socio-economic and
demographic characteristics of individual residents. Our findings are
consistent with the view that certain features of the built environment are
associated with worse mental health. These findings also are in keeping with
two prospective urban regeneration studies, which found associations between
improvements in the built environment and lower levels of anxiety and
depression (Halpern, 1995;
Dalgard & Tambs, 1997).
Although our findings must be viewed as preliminary, they support the view that social and physical incivilities, such as graffiti, vandalism and crime, may be associated with worse mental health among residents (Taylor et al, 1985; Perkins et al, 1993; Cohen et al, 2000). It should be noted also that there were negative findings, including the failure to find statistically significant associations with disused buildings or with areas in which properties mainly opened directly onto public space.
Understanding the effects of place on health
The mechanisms underlying our positive findings have yet to be elucidated,
and it remains unclear at what spatial level these and any other contextual
effects might occur (Wilkinson,
2000; Weich et al,
2001b). At a neighbourhood or small area level, the built
environment is likely to affect traffic, pollution, crime and residents'
perceptions about their own safety (Taylor
et al, 1985; Perkins
et al, 1993). There may also be effects on perceptions of
community spirit and other forms of social capital
(Birtchnell et al,
1988; Perkins et al,
1993; Sampson et al,
1997; Cohen et al,
2000). It has also been suggested that the built environment
modifies the effects of housing on health by affecting residents' perceptions
of their own dwellings (Kearns et
al, 2000).
It is perhaps easier to interpret associations between higher rates of depression and residence in areas characterised by graffiti, open spaces, dwellings with deck access and few private gardens than with areas characterised by properties of more recent construction. Many of the individual, household-level and area-level risk factors were correlated and (for example) those living in areas with post-1940s dwellings were more likely to be renting, to be living above the ground floor and to be in areas characterised by deck access dwellings. However, although properties built after 1969 might be viewed as a proxy for higher proportions of residents in rented and/or high-rise accommodation, the association with depression was not confounded to a statistically significant degree by individual socio-economic status or floor of residence. Moreover, this association remained statistically significant after adjusting for type of access to dwellings in the housing area.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication June 1, 2001. Revision received January 28, 2002. Accepted for publication January 30, 2002.
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