Social Psychiatry and Psychiatric Epidemiology
https://doi.org/10.1007/s00127-023-02575-0

RESEARCH

Increased urban greenspace in childhood associated with lower
inattention deficit among adolescents
Despina Bolanis1 · Massimiliano Orri2 · Francis Vergunst3 · Samantha Bouchard1 · Éric Robitaille4 ·Frederick Philippe5 · Isabelle Ouellet‑Morin6 · Alain Girard7 · Vincent Paquin2 · Lise Gauvin4 · Sylvana Côté4 ·Marie‑Claude Geoffroy2
Received: 3 February 2023 / Accepted: 28 September 2023
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany 2023

Abstract
Purpose There is a growing interest in assessing the benefits of exposure to urban greenspace on mental health due to theincreased urbanization of youth and concerns for their mental health. We investigated the prospective associations of residential greenspace in childhood and mental health in adolescence. Use of a well-characterized birth cohort permitted adjustment
for a range of potential confounding factors including family and neighborhood characteristics in addition to prior mental
health problems, and exploration of moderation effects by sex and family socioeconomic status.
Methods We analyzed longitudinal data collected from 742 urban-dwelling participants of the Quebec Longitudinal Studyof Children Development. The Normalized Difference Vegetation Index (NDVI) within 250, 500, and 1000 m buffer zones
surrounding the home residence was used to indicate childhood exposure to greenspace. Six self-reported mental healthproblems at 15/17 years were examined using the Mental Health and Social Inadaptation questionnaire: inattention, hyperactivity/impulsivity, conduct, depression, anxiety, and suicidal ideation.
Results Childhood urban greenspace was associated with lower inattention problems in both females and males. We observed
a 0.14 reduced standard deviation (SD) (β = − 0.14, SE = 0.05, p < 0.01) in relation to an interquartile range (IQR) increase
of NDVI (0.15) at the 250 m buffer zone, and similar results were found in 500 m and 1000 m buffer zones. These associations only slightly attenuated after adjustment for individual (sex, childhood mental health), family (family SES, maternal
age at birth, parental mental health, family composition), and neighborhood (material and social deprivation) characteristics(β = − 0.13, SE = 0.06, p = 0.03). No association was found for other mental health problems, and no moderation associationsof sex or family socioeconomic status were observed.
Conclusion These findings suggest that increasing residential greenspace in cities may be associated with modest benefits
in attentional capacities in youth, necessitating further research to elucidate the underlying mechanisms.
Keywords Greenspace exposure · Residential · Mental health · Youth
Abbreviations
NDVI	Normalized difference vegetation index
IQR	Interquartile range
SD	Standard Deviation
ADHD	Attention-deficit hyperactivity disorder

Introduction* Marie‑Claude Geoffroy
marie-claude.geoffroy@mcgill.ca

4Department of Social and Preventive Medicine, Universityof Montreal, Montreal, QC, Canada

5

Department of Psychology, University of Quebec
at Montreal, Montreal, QC, Canada

6

School of Criminology, University of Montreal, Montreal,
QC, Canada

7

CHU Sainte-Justine Research Center, Montreal, QC, Canada

1

Department of Educational and Counselling Psychology,
McGill University, Montreal, QC, Canada

2

Department of Psychiatry, McGill University, Montreal, QC,
Canada3

Special Needs Education, University of Oslo, Oslo, Norway

Approximately 1.2 million Canadian youth are affected byat least one mental health problem [1] with the prevalenceof depression and anxiety on the rise [2]. These alarming

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Social Psychiatry and Psychiatric Epidemiology

numbers bring to light the importance of identifying modifiable protective factors that could aid in alleviating mental
health problems.
In recent years, the potential benefits of exposure togreenspace (i.e., natural or semi-natural outdoor area completely or partially covered by vegetation, such as parks, forests, trees, and woodlands [3]) for mental health have gained
significant attention [4–6], especially for urban dwellers who
are more likely to benefit from greenspace (in comparison
with those residing in rural areas) as evidenced in a recent
review [7]. The promotion of greenspace in urban landscapes
may hold the potential to improve health since greenspaceoffers opportunities to reduce exposure to harmful exposures(e.g., air and noise pollution), restore attentional capacities,
and encourage physical activity [8].
Prospective population-based studies are imperative toassess the long-term associations between greenspace andmental health, especially as they allow for the examinationof individuals exposed to settings differing in levels of surrounding greenspace (most commonly measured using theNormalized Difference Vegetation Index (NDVI) [9]) overlong follow-up periods, and provide the ability to control for
key confounding factors assessed prior to the exposure (e.g.,childhood and parental mental health problems).
While some longitudinal population-based studies havefound that increased greenspace exposure in childhood is
associated with lower symptoms of depression [10, 11], anxiety [12], attention-deficit hyperactivity disorder (ADHD)[12–14], and conduct problems [12] in adolescence, otherstudies have not [15–17]. It is unclear whether or not thebenefits of greenspace exposure on mental health affect all
youth equally, and if some groups (such as female vs. male,or socioeconomically advantaged vs. disadvantaged youth)
benefit more than others. With respect to sex, some studies
indicate associations between increased greenspace exposure and lower mental health problems among male, but
not female individuals [18], whereas other studies report
inversed patterns of findings [14], or no differences [12,19]. Although the mechanisms by which sex modifies theassociations between greenspace and mental health remain
unknown, previous systematic reviews have posited thatphysiological and psychological responses to greenness
may differ across female and male individuals [20, 21]. At
the same time, it has been suggested that individuals withmental health problems from disadvantaged socioeconomic
backgrounds disproportionately benefit from higher greenspace exposure [22–25]; however, the few studies that investigated this question in youth have produced inconsistent
results [13, 14, 26–29]. Additionally, several studies reportassociations between higher levels of residential greenspaceand lower incidence of suicidal ideation and suicide mortality among adults [30–32]; however, evidence drawn fromadolescent populations is scarce [33].

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Drawing from a representative sample of adolescents
residing in urban regions of the province of Québec (Canada), this study had two aims. First, we aimed to investigate the associations of childhood residential greenspacewith a range of mental health problems (i.e., inattention,
hyperactivity/impulsivity, conduct problems, depression,anxiety, and suicidal ideation) with adjustment for factors
at the individual, family, and neighborhood levels. Second,
we examined whether these associations were moderated
by sex and by disparities in levels of family socioeconomic
status (SES).

Methods
ParticipantsParticipants were from the Québec Longitudinal Study ofChild Development (QLSCD; conducted by Institut de laStatistique du Québec, ISQ), a population-based birth cohortof 2120 children born in Québec, Canada, in 1997–1998 andfollowed up annually or biannually since [34]. The Québec
Master Birth Registry of the Minister of Health and Social
Services was used to create a stratified random sample
based on living area and birth rates [35]. At its inception,
the QLSCD represented the Québec population of singleton
births, including all ranges of socioeconomic status (SES).
More information regarding the QLSCD can be found on
https://​www.​iamil​lbe.​stat.​gouv.​qc.​ca/​defau​lt_​an.​htm. The
QLSCD protocol was approved by the Institut de la statistique du Québec and the St-Justine Hospital Research Centre
ethics committees, and informed consent, assent, or bothwere obtained at each data collection.

Procedure
We used information on childhood residential greenspace at
10 years of age (2008) and mental health outcomes reportedby the adolescents via an online questionnaire at 15 and17 years of age (2013/2015) [36–38]. We selected children
who were residing in urban regions of Québec (i.e., Montreal, Sherbrooke, Trois-Rivières, Gatineau, and Saguenay;
population size > 100,000 habitants per region, except Montreal with > 3 million habitants) in 2006/2008, accountingfor 65% of all children participating in the QLSCD.

Adolescent mental health problems
Mental health symptoms in the past year were assessed using
the Mental Health and Social Inadaptation Assessment for
Adolescents [39] (never = 1; sometimes = 2; often = 3). Adolescents self-reported externalizing problems, namely inattention, hyperactivity/impulsivity, and conduct problems,Social Psychiatry and Psychiatric Epidemiology

and internalizing problems, namely depression, generalized
anxiety, and serious suicidal ideation (“did you ever seriously think of attempting suicide?”; yes = 1, no = 0). The six
scales were z-standardized (Mean = 0, SD = 1) and averaged
across the two assessments to obtain a summary score foreach problem during adolescence (i.e., 15 and 17 years). The
items comprised in these scales, their internal consistencies,
and their correlation matrix are presented in Supplementary
Tables S1 and S2.

2120 enrolled in QLCSD in
1997/98• 942 (38.2%)

1526 (61.8%) children withpostal code information in2006 or 2008

• 525 (35.0%)Childhood residential greenspace
We retrieved the residential greenspace measure from the
Canadian Urban Environment Health Research Consortium
which was characterized using the Normalized Difference
Vegetation Index (NDVI). NDVI quantifies vegetation bymeasuring the ratio between near-infrared light, which
vegetation reflects, and red light, which vegetation absorbs[40]. Values from this index range between − 1 and 1, withnegative values representing water and/or cloud covering
and/or inorganic objects, values around zero representing
sparse and brown vegetation, and higher positive values representing dense and green vegetation. We used NDVI datafrom 2007 provided by the United States Geological Survey
Landsat 8 satellite, with a spatial resolution of 30 m accessed
via Google Earth Engine [41–44]. Given substantial snow
covering during the winter months in Québec, pixels withmore than 20% cloud or snow were not included in the NDVI
calculation and all bodies of water were masked.
NDVI values were available for 2007, and six-digit postal
code information for QLSCD participants was available in2006 and 2008. As such, we geocoded the NDVI values
in 2007 with the children’s six-digit postal codes in 2008
or 2006 for the 71 participants with missing postal code
information in 2008 (correlation between NDVI values
from postal code information in 2008 and 2006 was 0.89,
p < 0.001; Fig. 1), resulting in a cross-sectional NDVI
assessment. The six-digit postal code is the most precise
unit in Canada that allows for the identification of whereindividuals reside [45]; in urban regions, this is equivalent
to one side of a city block (e.g., single apartment building) [46]. In the current study, there was no clustering ofparticipants within six-digit postal codes (i.e., more than
98% of postal codes had a single participant allocated to it).
Greenspace data were abstracted to produce measures corresponding to circular buffers of 250 m, 500 m, and 1000 m
around the centroid of each child’s residential postal code.
Our main analysis relied on the 250 m buffer, and we modeled the maximum annual mean value obtained from acrossa series of pixels each having their own annual mean within
this buffer. We also conducted sensitivity analyses using
similarly derived maximum annual mean values with 500 m
and 1000 m buffers.

participants
missing postalcodes

977 (65.0%) children living
in urban regions of Québec
includedchildren living inrural regions ofQuébec excluded• 18 (1.8%) children
missing NDVI
information

959 (98.2%) children’s
postal codes matched withNDVI values in urban
regions of Québec

742 (77.3%) children
living in urban regions ofQuébec with self-reported
mental health problems inadolescence included in
final analyses• 235 (22.7%) withmissing
information on
mental health ineither 2015 or
2017

Fig. 1  Flowchart of participants in the QLSCD cohort used in the
study. Note: Data were compiled from the final master file of the
Québec Longitudinal Study of Child Development (1998–2017),©Gouvernement du Québec, Institut de la statistique du Québec.
Geographical region classification was calculated with Canadian census data in 2006 [47] based on all six-digit postal codes in Québec
which were then matched to the six-digit postal codes of participantsin the QLCSD. Participants residing in rural regions of Québec (i.e.,
regions with 10 000 to 100 000 residents) accounted for 35.0% of thecohort and were excluded from this study. QLSCD = Québec Longitudinal Study of Child Development

Confounding factors
Confounding factors were selected based on their associations with mental health and/or greenspace exposure (Supplement Table S3) and were measured at 8 and 10 years ofage with scores averaged across assessments (to maximize
the total sample size), unless otherwise indicated.

Individual characteristics
Child sex (male/female) was reported by parents. Childhood
mental health problems were reported by school teachers
using the Social Behavior Questionnaire [48]: oppositional

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Social Psychiatry and Psychiatric Epidemiology

and defiant behavior (four items; e.g., defiant or refused tocomply), inattention and hyperactivity (nine items; e.g.,“could not sit still”), and depressive and anxious symptoms(five items, e.g., fearful or sad). The items were derived
from the Canadian National Longitudinal Study of Children
and Youth [49], which incorporates items from the Child
Behavior Checklist [50], with responses rated on a threepoint scale.

Family characteristics
Maternal age at childbirth was recorded in years. Parental depressive symptoms in past week were assessed at
5 months using 12 items from the short form of the Centre
for Epidemiological Study Depression Scale (12 items; e.g.,“I felt depressed”) [51]. Parental antisocial behaviors duringadolescence were assessed using five retrospective conduct
items (e.g., having been in > 1 fight that they started; having
stolen > 1 time) [52]. For all parental mental health problems, a mean score was derived based on the availabilityof data from at least one parent. SES was measured using astandardized aggregate index of five items relating to parents’ education level, occupational prestige, and gross annual
household income [53]. The scale ranged from -3 to 3, centered at 0, with higher scores indicating higher SES. Family
composition was categorized as intact (biological parents) or
non-intact (single, separated, divorced, or widowed).

which allowed us to identify participants’ socioeconomic
characteristics based on their neighborhood area.

Statistical analyses
Analyses were conducted using SPSS (version 27). First,
we examined the sample characteristics using means or
frequencies. Second, we examined the association between
greenspace and mental health problems using linear regression for continuous outcomes and logistic regression for suicidal ideation adjusting for identified individual, family, andneighborhood characteristics. Associations were expressedin relation to one interquartile range (IQR) increase in the
250 m buffer of childhood residential greenspace. The IQR
for the childhood residential greenspace metric (maximumof surrounding annual mean NDVI values within the 250 m
buffer) was 0.15. Mental health problems outcomes werestandardized (mean, 0; SD, 1) so that the regression coefficient (β) represents the standard deviation (SD) increasein symptoms associated with each IQR increase in greenspace. Third, to test whether sex and/or SES moderated theassociations between greenspace exposure and mental healthproblems, interaction terms for these variables were examined separately in the fully adjusted models. Statistical significance was set at p < 0.05, and all tests were two-tailed.

Results

Neighborhood characteristics

Sample characteristics

Neighborhood socioeconomic disadvantage was estimatedusing material and social deprivation indices based on census data [54], consistent with approaches used in previous
studies [55–58]. These deprivation indices are based on data
aggregated at the dissemination area level, which represents
the smallest spatial unit available from census data in 2006
(in urban areas this is equivalent to an average of 400–700
individuals residing in one or more neighboring blocks ofhouses). They were constructed using a principal component
analysis that integrated six census variables into two components (material and social). The material deprivation index
is computed based on the proportion of individuals withouta high-school diploma, their average personal earnings, andthe employment–population ratio at the dissemination arealevel. The social deprivation index is computed from the
proportions of individuals, respectively, living alone, heading a single-parent family, and being separated, divorced,
or widowed. Both material and social deprivation indiceswere categorized into quintiles of equal population size,
ranging from the most privileged (first quintile) to the mostdeprived (fifth quintile). We linked the children’s six-digit
postal code data with the corresponding dissemination area

Of the 2120 participants recruited at baseline, 1526 children
participated in data collection in 2006 or 2008 and provided
information on their postal code, of whom 959 were living inurban regions. Of them, 742 participants (77.3%) provided
information pertaining to mental health problems (Fig. 1).
Key characteristics of the 742 participants are shown in
Table 1. Participants residing in urban areas but who were
not included in the study sample (n = 235) were more
likely to be male (131/235 [55.7%] for those excluded fromanalyses vs. 336/742 [45.2%] for those included in analyses, χ2 = 7.83, p = 0.005); their mothers had more depressive symptoms at birth (1.52 vs. 1.30 [on a scale from 0
to 10], t­971 = 2.23, p = 0.026); and their parents had lower
socioeconomic status at 5 months (z scores − 0.22 vs. 0.07,
t970 = − 3.95, p < 0.001; Supplement Table S4).

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Associations of childhood greenspace with mental
health problems and moderations by sex and family
SES
In the unadjusted model, an interquartile range increase inchildhood greenspace exposure (0.15; 250 m buffer) wasSocial Psychiatry and Psychiatric Epidemiology
Table 1  Key characteristics of 742 participants from the QLSCD surveyed at ages 15 to 17 years in 2013 or 2015 and greenspace exposure
at age 10 years in 2006 and 2008
Variables

Study sample
M (SD)

Adolescent mental health problems
Conduct problems
Inattention
Hyperactivity/impulsivity
Depression
Anxiety
Suicidal ideation
Yes
No
Childhood NDVI (250 m)
Individual level
FemaleMaleChildhood conduct problems
Childhood ADHD
Childhood depression/anxiety
Adolescent ritalin ­usea
Yes
No
Family level
Maternal age
Parental depression
Parental antisociality
Parental socioeconomic status
Family composition
IntactNot intact
Neighborhood level
Material ­deprivationa
Most privileged
Most deprived
Social ­deprivationb
Most privileged
Most deprived

N (%)

0.74 (0.86)
3.37 (1.81)
2.61 (1.57)
3.62 (2.01)
4.31 (1.97)

3.24 (0.66)

1.53 (0.77)
2.67 (2.39)
2.12 (1.96)

73 (9.8)669 (90.2)

406 (54.7)
336 (45.3)

95 (13.2)
627 (86.8)
30.19 (4.94)
1.18 (0.91)
0.20 (0.96)
0.41 (0.54)521 (70.2)
221 (29.8)

253 (34.1)
74 (10.0)
191 (25.7)
108 (14.6)

Data are n(%) or mean (SD). NDVI = Normalized Difference Vegetation Index. The Mental Health and Social Inadaptation Scale [39] wasused to assess mental health problems; however, these measures did
not provide clinical diagnoses, but rather assessed severity of symptoms. Data were compiled from the final master file of the Québec
Longitudinal Study of Child Development (1998–2017), ©Gouvernement du Québec, Institut de la statistique du Québec. NDVI
metrics, indexed to DMTI Spatial Inc. postal codes, were provided by
CANUE (Canadian Urban Environmental Health Research Consortium)ab

Maximum available data were N = 722

Only data in the extreme categories are reported (first quintile = mostprivileged; fifth quintile = most deprived)

associated with 0.14 SD decrease in adolescent inattention(β = − 0.144, SE = 0.055, p < 0.01). This association persisted in the fully adjusted model with control for individual,family, and neighborhood characteristics, wherein an interquartile range increase in childhood greenspace exposure(0.15; 250 m buffer) was associated with 0.13 SD decreasein adolescent inattention (β = − 0.126, SE = 0.059, p = 0.032;
Fig. 2A; Supplement Table S5). To verify the robustness of
the results, sensitivity analyses were conducted to examine
the (1) extent to which prescribed adolescent Ritalin use
at 15/17 years of age may impact the association between
greenspace exposure and ADHD and (2) whether or notimportant variations in the strength of association between
greenspace exposure and mental health varies across different distance buffers (500 m and 1000 m). First, additional
adjustment for adolescent past-year use of Ritalin (13.2%
of sample) did not attenuate the association between childhood greenspace exposure and inattention (β = − 0.128,
SE = 0.060, p = 0.032). Second, similar pattern of results
were observed across the three buffers for the association
between greenspace exposure and inattention (see Supplement Tables S6 and S7).
No significant associations between childhood
greenspace exposure and externalizing (conduct;
β = − 0.021, SE = 0.058, p = 0.715, hyperactivity/impulsivity; β = − 0.044, SE = 0.058, p = 0.447) and internalizing (depression; β = 0.021, SE = 0.055, p = 0.704, anxiety;β = − 0.017, SE = 0.056, p = 0.761, and suicidal ideation;
odds ratio [OR] = 1.25, 95%CI [0.83,1.89]); Fig. 2B–F; Supplement Table S5) mental health problems were observed inadolescence, for both sexes combined.
Overall, associations between greenspace exposure andmental health problems were not moderated by child’s
sex (ps > 0.05), except for a significant greenspace-by-sex
interaction for conduct problems (β = − 0.167, SE = 0.075,
p = 0.025) at the 250 m buffer, suggesting associations
between higher greenspace and lower conduct problems infemale (β = − 0.130, SE = 0.076, p = 0.088), but not in male(β = 0.107, SE = 0.082, p = 0.193) participants. However, thisgreenspace-by-sex interaction for conduct problems was not
replicated at the 500 m and 1000 m buffers (Supplement
Tables S6 and S7). There were no significant interactions
between childhood greenspace exposure and SES for any
mental health problems (ps > 0.05).

Discussion
This study examined associations between childhood urban
greenspace exposure and a range of mental health problems in adolescence. After adjustment for characteristics at
the individual, family, and neighborhood levels, including
prior childhood mental health problems and socioeconomic

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Social Psychiatry and Psychiatric Epidemiology

Fig. 2  Associations between residential greenspace exposure (250 m)
at age 10 years with adolescent mental health problems at either 15
to 17 years among 742 participants from the ­QLSCDa,b. Note: Analyses for inattention, impulsivity/hyperactivity, conduct, depression,anxiety, and suicidal ideation problems were conducted on the fullsample as there was non-significant greenspace-by-sex interactions(ps > 0.05). Across all mental health problems, there were no significant greenspace-by-SES interactions (ps > 0.05). Note: Individual
characteristics included sex and childhood mental health problems.

Family characteristics included maternal age, parental mental health,socioeconomic status, and family composition. Neighborhood characteristics included material and social deprivation [54]. aData werecompiled from the final master file of the Québec Longitudinal Studyof Child Development (1998–2017), ©Gouvernement du Québec,Institut de la statistique du Québec. bNDVI metrics, indexed to DMTI
Spatial Inc. Postal codes were provided by CANUE (Canadian Urban
Environmental Health Research Consortium)

characteristics, we found an association between greenspace exposure and reduced inattention problems in bothmales and females. We found no evidence of an association
between greenspace exposure and adolescent hyperactivity/
impulsivity, conduct, depression, anxiety, and suicidal ideation problems, and sex and family SES did not consistently
moderate any of the associations.

residential greenspace were associated with fewer symptomsof ADHD throughout childhood and adolescence in both
females and males. Moreover, in another sample of 57,450
New Zealand youth followed from ages 2–18 years, those
exposed to increasing levels of neighborhood greenspace
throughout their lives had a lower incidence of being diagnosed with ADHD before 18 years of age [13]. Conversely,
in a sample of youth from England, increasing levels of residential greenspace was associated with lower levels of inattention, although these associations were better explainedby socioeconomic status [62].
To the best of our knowledge, our study was the first to
examine the strength of associations for the full spectrumof ADHD-specific problems (inattention vs hyperactivity/
impulsivity) which builds on prior research by showingthat childhood greenspace exposure was associated withlower levels of inattention in females and males, but not

Greenspace and ADHD
Our findings showing associations between childhood
greenspace and lower inattention problems are in line withcurrent knowledge summarized in systematic reviews [59,60] including a few longitudinal studies [13, 14, 61, 62].
Consistent with the findings from our study, two longitudinal studies based on prospective cohorts from Germany
and Denmark [14, 61] showed that increasing levels of

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Social Psychiatry and Psychiatric Epidemiology

hyperactivity–impulsivity problems. There are brain mechanism differences demonstrated in youth presenting with profiles of combined ADHD vs profiles of inattentive or hyperactive–impulsive problems only [63]. In the present study,
the potential restorative qualities of greenspace exposure
were observed for inattention problems across a variety of
buffer zones (250 m, 500 m, 1000 m). These results are inline with one robust randomized control study which demonstrated that youth diagnosed with ADHD (n = 17) had better
attention (assessed with the digit span backwards, a standardized measure of concentration) after walking in a park,in comparison with when they walked in an urban neighborhood, and the benefits of walking in a park in improving
attention were large (Cohen’s d = 0.77) [64]. These results
echo those from a large observational study of children(7–10 years of age) residing in Spain that illustrated how
over a 12-month period, children residing in the greenest
neighborhoods improved their attentional capacities assessed
via a computerized attentional task [29].

Greenspace and other mental health problems
Our study showed no significant associations between childhood greenspace exposure and depression and anxiety inadolescence. These results are consistent with another longitudinal study of American adolescents that indicated thatchildhood greenspace exposure was not associated with selfreported symptoms of anxiety and depression in adolescence[65]. Conversely, other longitudinal studies have shown that
increased childhood greenspace exposure was associatedwith fewer symptoms of depression [66] and anxiety [12] inadolescence, although these studies used other greenspace
metrics than NDVI as was utilized in our study. It has been
illustrated that different greenspace metrics yield differing
associations between greenspace exposure and mental healthoutcomes [67, 68].
Our finding that childhood greenspace was not associated with suicidal ideation in adolescence is in line with aprevious study that evaluated associations between school
surrounding greenspace and suicidal ideation in youth [33].
However, other studies based on adult populations [30, 31]
have demonstrated that increased level of residential greenspace is linked to decreased risk of suicide mortality. It may
be that greenspace exposure affects suicidal ideation andsuicide mortality differently.
For conduct problems, our findings suggesting reduced
symptoms among females (not males) exposed to higher levels of greenspace at the 250 m buffer should be interpretedwith caution, as this result was not replicated within the
500 m and 1000 m buffer zones. Additionally, longitudinal studies have yielded mixed results [16, 26, 28]. On the
one hand, a study of 1287 American adolescents indicatedthat more residential greenspace was associated with fewer

aggressive symptoms in late adolescence [26]. On the other
hand, a study of 715 Dutch adolescents reported no significant associations between surrounding residential greenspace and conduct problems when adolescents reached young
adulthood [16]. In contrast to our findings that higher levelsof surrounding greenspace were associated with fewer conduct problems in females, a study of 2909 Scottish children
indicated that closer proximity to parks was associated withfewer conduct symptoms in boys, but not in girls [28]. However, this study measured greenspace in terms of the proximity to parks, rather than the level of surrounding residential
greenspace, as measured in our study.

Socioeconomic inequalities in the distributionof greenspace
In line with studies from other countries, our results revealed
socioeconomic inequalities in the distribution of greenspace, with children growing up in socioeconomically disadvantaged families being more likely to live in areas withlower levels of greenspace. Nevertheless, we did not findthat greenspace was more beneficial for mental health problems of the most socioeconomically disadvantaged youth,
as shown elsewhere [13, 14, 27].

Potential mechanisms
Greenspace exposure may protect youth’s mental healthdue to three major reasons. First, increased greenspace canreduce stress (e.g., cortisol) and increase attention, self-control, and problem-solving capacities, ultimately promoting
the restoration of psychological well-being [4]. The “Attention Restoration Theory” posits that natural green environments diminish mental fatigue thus increasing attentional
capacities [69]. Second, urban environments are notorious
for emitting air and noise pollutants which can have adverse
consequences for mental health [70, 71]. Increased greenspace in urban settings provides the potential to mitigate
major pollutants, as natural environments are not generally
pollutant emission sites. Third, contact with greenspacestrengthens psychosocial adaptation by encouraging physicalactivity and social connection, both of which are protective
factors for mental health [72, 73].

Methodological considerations
This study has several strengths, including its prospective
design with greenspace exposure assessed in childhood anda wide range of mental health outcomes in adolescence. The
use of a well-characterized cohort permitted the inclusionof several confounding factors at differing levels, including adjustment for prior mental health problems assessedin childhood. We also evaluated our associations between

13Social Psychiatry and Psychiatric Epidemiology

mental health and greenspace exposure across three circular buffer zones (250 m, 500 m, 1000 m). However, some
limitations should also be highlighted. First, although NDVI
objectively quantifies the level of surrounding greenspacein a given area, it does not capture the quality, access, anduse of greenspace, which has been previously associatedwith improved mental health in youth [74, 75]. Additionally, the present study examined residential greenspace only,
while other greenspace exposure contexts, such as the school
environment, may also impact mental health [33]. Second,surrounding greenspace was estimated at one time point inchildhood and did not allow for an evaluation of the cumulative effects of greenspace exposure throughout childhood
which may have underestimated the total greenspace exposure for a given participant over time [76, 77]. Future studies
could examine the extent to which change in greenspace
exposure overtime is associated with change in mental healthsymptom severity. Third, mental health problems were selfreported by adolescents which does not provide a clinicaldiagnosis for mental health problems, although the measure used [39] does cover a large spectrum of mental healthsymptoms based on DSM-5 criteria. Fourth, the presenceof potential unmeasured confounding factors is a limitationof this work, although we did adjust our analyses for individual, family, and neighborhood characteristics, consistent
with previous studies [62, 78] and extending prior knowledge by adjusting for childhood mental health problems andparental depressive symptoms and antisocial behaviors. Of
note, ethnicity and racism have been shown to intersectwith environmental exposures and health [79], but there
were insufficient data on these factors to adequately adjust
for them in the QLSCD. Fifth, while psychometric properties are acceptable, the internal consistency for inattention
problems (15 years α = 0.66, 17 years α = 0.68) was close
but below the conventional 0.70 threshold [80], suggesting that these results may need to be interpreted cautiously.
While the present study did not find differences in the associations by sex, future studies could examine whether sex/
gender potentially modify associations between greenspace
exposure and mental health. Sixth, attrition occurred among
potentially at-risk individuals, such as those from lower
SES backgrounds, children of mothers with more depressive symptoms at birth, and male participants; which may
have resulted in a selection bias and an underestimation of
associations for these individuals.

Conclusion
Our longitudinal study revealed that higher levels of urban
residential greenspace were associated with lower levels
of inattention problems in male and female youth from allsocioeconomic backgrounds. This finding along with other13

studies [14, 61] further highlights the importance of promoting the development of urban greenspace infrastructuresto protect youth mental health. Although more studies areneeded to elucidate the pathways by which greenspace benefits attentional abilities in youth, results from this study
underscore the importance of promoting urban greenspacesuch as parks, gardens, street trees, or private backyards.
Nevertheless, urban planning decisions may also consider
other aspects of greenspace such as quality, quantity, andaccessibility, which are also known to bring health benefits[74, 75].
Supplementary Information The online version contains supplementary material available at https://d​ oi.o​ rg/1​ 0.1​ 007/s​ 00127-0​ 23-0​ 2575-0.
Author contributions Ms. Bolanis and Dr. Geoffroy conceptualized anddesigned the study, conducted the analyses, drafted the initial manuscript, reviewed and revised the manuscript, had full access to the data
used in this study, and took responsibility for the integrity and accuracy of the data analysis; Drs. Orri, Vergunst, Philippe, Ouellet-Morin,
Paquin, Ms. Bouchard, and Mr. Girard participated in the analysis andinterpretation of data, drafted the initial manuscript, and reviewed andrevised the manuscript for important intellectual content; Drs Robitaille, Gauvin, and Côté reviewed and revised the manuscript for important intellectual content; and all authors approved the final manuscript
as submitted and agree to be accountable for all aspects of the work.
Funding Mrs. Bolanis was funded by the Canada Graduate Scholarships Doctoral (CGS-D) Program for the Social Sciences and Humanities Research Council (SSHRC). Drs Ouellet-Morin and Geoffroy eachhold a Canada Research Chair. This study was conducted with funding
from the SSHRC (Drs Geoffroy, Philippe and Ouellet-Morin) and the
Research team in suicide prevention Fonds de Recherche du Quebec–
Société et Culture–Papageno (Drs Geoffroy and Orri). The Québec
Longitudinal Study of Child Development was supported by funding
from the ministère de la Santé et des Services sociaux, le ministère dela Famille, le ministère de l’Éducation et de l’Enseignement supérieur,
the Lucie and André Chagnon Foundation, the Institut de recherché
Robert-Sauvé en santé et en sécurité du travail, the Research Centreof the Sainte-Justine University Hospital, the ministère du Travail, del’Emploi et de la Solidarité sociale, and the Institut de la statistique duQuébec. Additional funding was received by the Fonds de Recherche
du Québec-Santé (FRQS), the Fonds de Recherche du Québec-Sociétéet Culture (FRQSC), the Social Science and Humanities ResearchCouncil of Canada (SSHRC), and the Canadian Institutes of HealthResearch (CIHR).
Data availability Data have been obtained from a third party. The data
analyzed in this study were obtained from the Institut de la statistiquedu Québec, and as stipulated in clauses 10 and 11 of the Institut de lastatistique’s du Québec Act (Canada), the access to the data is restricted
to the parties identified in the partnership agreement signed to ensure
the conduct of the study and which describes the author’s right. In the
QLSCD cohort, the participants only consented to share their data
to the study’s financial partners and affiliated researchers and theircollaborators. Those partners and researchers only have access after
signing a data sharing agreement. Requests to access these data canbe directed to the Institut de la statistique du Québec’s Research Data
Access Services – Home (www.​quebec.​ca).

Declarations
Conflict of interest There are no conflicts of interest to disclose.

Social Psychiatry and Psychiatric Epidemiology

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