Vol.3, No.1, 104-110 (2013) Open Journal of Preventive Medicine
http://dx.doi.org/10.4236/ojpm.2013.31013
Development of health and depressive symptoms
among Danish adolescents—Socioeconomic
differences and effects of life-style
Johan Hviid Andersen1, Merete Labriola1,2*, Thomas Lund1,3, Claus D. Hansen1,4
1Danish Ramazzini Centre, Department of Occupational Medicine, Regional Hospital Herning, Herning, Denmark;
*Corresponding Author:
2Department of Clinical Social Medicine, Public Health and Quality Management, Central Denmark Region and Section of Clinical
Social Medicine & Rehabilitation, School of Public Health, University of Aarhus, Aarhus, Denmark
3National Centre for Occupational Rehabilitation, Rauland, Norway
4Department of Sociology & Social Work, Aalborg University, Aalborg, Denmark
Received 19 November 2012; revised 20 December 2012; accepted 28 December 2012
ABSTRACT
While the existence of social inequality in health
in childhood as well as among adults is well es-
tablished, research of mechanisms underlying
this inequality is still sparse. The study aim was
to report on the development of self-rated health
and depressive symptoms from age 15 to18
years in a cohort study of Danish adolescents.
Methods: The cohort comprised 3,681 individu-
als born in 1989, 3058 individuals answered the
baseline questionnaire in 2004, and 2400 re-
sponded to a follow-up questionnaire in 2007,
with 2181 individuals participating in both rounds
(59% of the original cohort). Social background
information of the participants was derived from
a national register. For the analysis two vari-
ables indicating change in the two health indi-
cators was computed by subtracting the 2007
levels of the variables from the levels experi-
enced in 2004. Results: After 3 years, mean
self-rated health (SRH) deteriorated slightly in
adolescents (−0.24; 95% CI = −0.28 to −0.19)
across all socioeconomic status (SES) groups
and depressive symptoms increased (0.64; 95%
CI = 0.52 to 0.75). High household income was
protective for decrease in SRH (0.62; 0.43 - 0.91).
Negative life-style changes were associated with
poorer SRH and more depressive symptoms.
Conclusions: Self-rated health and depressive
symptoms changed to the worse among Danish
adolescents from age 15 to 18 years. Negative
changes in several lifestyle factors were found
to accompany the deterioration of health. This
result stresses the intrinsic relationship be-
tween lifestyle changes and health and the pos-
sible positive effect of maintaining and enhanc-
ing positive lifestyle factors.
Keywords: Longitudinal Cohort Study; Lifestyle;
Self-Rated Health; Depressive Symptoms
1. INTRODUCTION
Whilst social inequality in childhood and adult health
is well established, research into the mechanisms under-
lying this inequality is essential if we are to understand
how social and economic factors are related to health and
where interventions will be effective. Assessments of
individual overall health status have been widely studied
by means of self-rated health (SRH), originally devel-
oped for the ShortForm-36 (SF-36) and SF-12. In adult
populations, this single self-perception measure has re-
vealed systematic associations with later morbidity,
mortality and disability [1,2]. Despite a large body of
work examining adult SRH, only a few studies have
evaluated the role of SRH among adolescents as a meas-
ure of actual health status.
Among US adolescents’ self-rated health was found to
be moderately stable and was characterized as an endur-
ing self-concept among adolescents [3]. The Norwegian
young-Hunt study followed adolescents aged 13 - 19
years for 4 years and found that SRH was a relatively
stable construct during adolescence and that it was re-
lated to both general well-being and disability as well as
to use of healthcare, and health-compromising behav-
iours. The study, however, lacked information on family
income and parents’ educational level rendering socio-
economic comparisons impossible [4].
The German Bella-study [5] found children from
lower social status homes to report a lower health-related
quality of life compared to children from middle social

J. H. Andersen et al. / Open Journal of Preve ntive Medicine 3 (2013) 104-110 105
status homes, who, in turn, were surpassed by children
with a high family social status. Various mechanisms
that could explain the relationship between socioeco-
nomic status, and the well-being and health-related qual-
ity of life of children and adolescents are being widely
discussed in the literature [6-10]. Many of the hypothe-
sized mechanisms refer to differences in access to mate-
rial and social resources or to reactions to stress-induced
conditions to which children and adolescents are exposed.
One of the most prominent explanations of social ine-
quality of health is the behavioural/cultural explanation
that hypothesize that the observed health differentials are
primarily the result of social class differences in health
related lifestyle behaviours [6].
Depression is another commonly studied measure of
health and wellbeing among adolescents and young
adults [11-15]. First onset is usually in adolescence
[11-12]. Depression early in life can have serious impli-
cations for the individuals’ school performance, school
absence and dropout and later professional careers [14].
Furthermore, depression in adolescence can increase use
of tobacco and alcohol [15]. Other studies have shown a
moderate association between physical activity and de-
pression amongst adolescents [16,17]. However, due to
cross sectional designs, the causal relation between de-
pression and physical activity is unclear.
This study reports on the development of self-rated
health and depressive symptoms, from age 15 to 18, in a
prospective cohort study among Danish adolescents. The
aim was to study life-style related predictors for health
change among children with different social backgrounds
defined by household income and parents’ education.
2. METHODS
2.1. Study Population
Data were gathered as part of the ongoing West Jut-
land Cohort Study (VestLiv), which is a survey follow-
ing a complete regional cohort of adolescents in the
Western part of Denmark, gathering comprehensive in-
formation on the occurrence, severity and impact of
manifold symptoms of physical and mental health prob-
lems—both self-reported and register-based [18]. Infor-
mation on socioeconomic status of parents is from offi-
cial registers.
The cohort comprised of 3681 individuals born in
1989, of which 3058 answered the baseline questionnaire
in 2004, resulting in a response rate of 83%. Everyone
who had not opted out of the study (N = 3293) was sent
the second round questionnaire in 2007, and 2400 an-
swered the questionnaire resulting in a response rate of
73%; 2181 individuals participated in both rounds (59%
of the original cohort). These 2181 individuals constitute
the basis of analysis in this study.
Information on the social background of the partici-
pants (e.g. household income, parents’ highest education
etc) derived from a national register in Statistics Den-
mark by using information from the Central Office of
Civil Registration (CPR) in which the respondents are
linked to their legal parents or guardians via a personal
identification number given to everyone in Denmark at
birth (or upon entry for immigrants).
Ethical approval: The study has been notified to and
registered by Datatilsynet (the Danish Data Protection
Agency). According to Danish law, questionnaire and
register-based studies do not need approval by ethical
and scientific committees, nor informed consent.
2.2. Health Indicators
This study examines two aspects of adolescents’
health status: self-rated health (SRH), and psychological
health. For SRH the question was “In general, how
would you rate your health?” with response options from
1 “Poor” to 5 “Excellent.” Psychological health was
measured using the Center for Epidemiological Studies
Depression Scale for Children (CES-DC), 4-item version
[19]. Responses were scored 0 “Not At All”, 1 “A Little”,
2 “Some”, 3 “A Lot”.
2.3. Independent Variables
Socioeconomic status (SES) was defined according to
household income and parents’ educational level in the
year before baseline (2003). Household income was di-
vided into quartiles, and parents’ highest education was
divided into four levels: under 10 years, 10 - 12 years, 13
- 15 years and >15 years of education.
Life-style factors were measured by a series of ques-
tions on leisure-time and sporting activities, smoking
habits, time spent watching television and using a com-
puter, and eating habits at age 15 and 18 years. We con-
structed dichotomous variables for a change in life-
style indicating a potentially negative change versus no
change/change to a healthier life-style during the 3-year
follow-up period e.g. starting smoking versus continuing
to smoke/stopping smoking. Characteristics of the study
population at baseline 2004 are described in Table 1.
2.4. Statistics
Adolescents who participated in both waves of the
study (2004 and 2007) were eligible for data analysis (n
= 2181). For the analysis, two variables indicating a
change in the two health indicators was computed by
subtracting the 2007 levels from the level reported in
2004. These are the dependent variables. A decrease of at
least one scale point on a scale from 1 to 5 was consid-
ered a relevant change for SRH, and for CES-DC scale,
which runs from 0 to 12, a change of at least 3 scale-

J. H. Andersen et al. / Open Journal of Preve ntive Medicine 3 (2013) 104-110
106
Table 1. Characteristics of study population at baseline 2004 and at follow up 2007, and changes in negative direction for included
variables from 2004 to 2007.
2004 2007 2004/2007
Variable Level N (%) N (%) N (%)
Gender Female 1180 (54.1)
Male 1001 (45.9)
Self-rated health (SRH) Excellent 645 (29.8) 477 (22.5)
Very good 999 (46.1) 909 (42.8)
Good 442 (20.4) 608 (28.6)
Fair 76 (3.5) 138 (6.5)
Poor 6 (0.3) 21 (1.0)
Poorer SRH at follow-up Decrease of ≥1 point 780 (35.8)
Depress. symptoms (score 0 - 12) 0 - 3 1665 (78.5) 1446 (67.1)
4 - 12 455 (21.5) 708 (32.9)
More depressive at follow up Increase of ≥3 point 465 (24.3)
Parental educational level <10 yrs 214 (9.8)
10 - 12 yrs 1107 (50.8)
13 - 15 yrs 709 (32.5)
>15 yrs 138 (6.3)
Household income, EURO <60,000 473 (21.7)
60 - 75,000 533 (24.4)
75 - 90,000 573 (26.3)
>90,000 590 (27.1)
Participation in sports, hrs/week 0 32 (1.5) 99 (4.6)
Approx. 0.5 84 (3.9) 102 (4.7)
Approx. 1 214 (9.8) 295 (13.6)
Approx. 2 - 3 565 (25.9) 668 (30.7)
Approx. 4 - 6 756 (34.7) 649 (29.8)
7 or more 511 (23.4) 360 (16.6)
Reduction in sports 338 (15.5)
Smoking habits Non smoker 1889 (89.2) 1555 (73.5)
<Once/week 94 (4.4) 158 (7.5)
Not daily, but >once/week 39 (1.8) 98 (4.6)
Daily 94 (4.4) 305 (14.4)
Begun to smoke 386 (17.7)
TV/video and computer use <2 hrs/day 913 (42.3) 470 (22.0)
2 hrs +/day 1246 (57.7) 1668 (78.0)
More TV and computer use 1435 (65.8)
Fruit/vegetable intake Once/day or more 849 (39.2) 310 (14.6)
Once or more/week 727 (33.5) 752 (35.4)
<Once/week 589 (27.2) 1061 (50.0)
Less fruit/vegetable 1,106 (33.7)
Wholegrain bread intake Once/day or more 645 (30.4) 667 (31.5)
Once or more/week 956 (45.0) 798 (37.6)
<Once/week 523 (24.6) 653 (30.9)
Less full grain bread 535 (24.5)

J. H. Andersen et al. / Open Journal of Preve ntive Medicine 3 (2013) 104-110 107
points, corresponding to 1 standard deviation, was used
to indicate change. Logistic regression analyses were
conducted with the two measures of SES, life style fac-
tors, and gender as the independent variables. Results are
reported as odds ratios (OR) with 95% confidence inter-
vals (95% CI) for developing poorer self-rated health and
more depressive symptoms in the 3-year follow-up pe-
riod. Baseline levels of the two outcomes and all the
life-style factors were included in the models in order to
adjust for baseline levels. The Hosmer-Lemeshow Good-
ness-of-fit test was used for each of the logistic regres-
sion models.
3. RESULTS
Assessments of health behaviour at baseline 2004 and
at follow up 2007 show changes in negative direction for
all included variables (Table 1).
Furthermore, mean self-rated health (SRH) deterio-
rated slightly in adolescents from 15 to 18 years (−0.24;
95% CI = −0.28 to −0.19) across all SES groups (Table
2) and depressive symptoms increased (0.64; 95% CI =
0.52 to 0.75) during the 3 years (Table 3)
Parental education level was not associated with a de-
terioration in SRH or increase in depressive symptoms
among adolescents from 15 to 18 years of age, whereas
there was a tendency for adolescents from lower income
homes to develop poorer SRH: Higher household income
was protective against reporting poorer SRH after 3
years (OR = 0.62; 95% CI 0.43 - 0.91), but had no effect
on the development of depressive symptoms. Female
adolescents had a two-fold risk of developing worse
SRH and more symptoms of depression in the 3-year
period compared to males (Table 4).
Changes in several of the life-style factors were asso-
ciated with poorer SRH in the follow-up period. Adoles-
cents who reduced their sporting activities (OR=1.97;
1.46 - 2.66) or decreased their intake of fruit and vegeta-
bles (1.36; 1.06 - 1.73) had poorer SRH after 3 years.
More than two thirds of the respondents (65.8%) had
increased their time with television and computer use,
and this was associated with poorer SRH (OR = 1.58;
1.23 - 2.02). A reduction in fruit and vegetable intake
and of whole-grain bread were each associated with a
48% increased risk of reporting more depressive symp-
toms after 3 years, whereas the association between
eating habits and SRH after 3 years was smaller (Tabl e
4). Finally, reducing sports activities was associated
with poorer SRH and more symptoms of depression
from age 15 to 18. Those who begun to smoke reported
poorer SRH (OR = 1.81; 1.36 - 2.42) at follow-up (Ta-
ble 4).
4. DISCUSSION
In general, development in self-rated health and de-
pressive symptoms were in a negative direction among
Table 2. Self-Rated Health (SRH) at baseline (2004) and follow-up (2007). N = 2140.
Follow-up 2007
Self-rated health*
Excellent Very good Good Not very goodPoor Total
Excellent 261 (12.2%) 262 (12.2%) 99 (4.6%) 14 (0.7%) 2 (0.1%) 638 (29.8%)
Very good 174 (8.1%) 479 (22.4%) 282 (13.2%) 41 (1.9%) 10 (0.5%) 986 (46.1%)
Good 34 (1.6%) 145 (6.8%) 191 (8.9%) 61 (2.9%) 5 (0.2%) 436 (20.4%)
Not very good 4 (0.29%) 18 (0.8%) 29 (1.4%) 20 (0.9%) 4 (0.2%) 75 (3.5%)
Poor 1 (0.1%) 1 (0.1%) 2 (0.1%) 1 (0.1%) 0 5 (0.2%)
Baseline 2004
Total 474 (22.2%) 905 (42.3%) 603 (28.2%) 137 (6.4%) 21 (1.0%) 2140 (100%)
*Mean change estimate; 95% CI, t-test p-value, All: −0.24; −0.28 to −0.19, p < 0.000. Scale range 1 - 5, Boys/girls: 0.06; −0.03 to 0.14, p = 0.09.
Table 3. Depressive symptoms at baseline (2004) and follow-up (2007). N = 2120.
Follow-up 2007
Depressive symptoms*
Scale score 0 to 3 Scale score 4 to 12 Total
Scale score 0 to 3 1197 (56.5%) 468 (22.1%) 1,665 (78.5%)
Scale score 4 to 12 227 (10.7%) 228 (10.8%) 455 (21.5%)
Baseline
2004
Total 1424 (67.2%) 696 (32.8%) 2120 (100%)
*Mean change estimate; 95% CI, t-test p-value; All: 0.64; 0.52 to 0.75, p < 0.000. Scale range 0 - 12; Boys/girls: 0.30; 0.07 to 0.52, p = 0.005.

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108
Table 4. Parental socioeconomic status (SES) and change in life-style factors-effects on the risk of developing poorer general health
and more depressive symptoms in a 3-year follow up period amongst Danish adolescents. Logistic regression with odds ratios (OR)
with 95% confidence interval (CI). N = 2181.
Poorer self-rated health More depressive symptoms
Variable Level N (%)
Partly adjusted*
OR; 95% CI
Fully adjusted**
OR; 95% CI
Partly adjusted*
OR; 95% CI
Fully adjusted**
OR; 95% CI
Up to 10 yrs 214 (9.9%) 1.00 1.00 1.00 1.00
10 - 12 yrs 1107 (51.1%) 0.89;
0.63 - 1.26
0.88;
0.59 - 1.31
0.87;
0.59 - 1.28
0.89;
0.58 - 1.37
13 - 15 yrs 709 (32.7%) 1.04;
0.72 - 1.50
1.07;
0.70 - 1.63
1.02;
0.68 - 1.55
1.13;
0.71 - 1.79
Educational level
>15 yrs 138 (6.4%) 1.10;
0.66 - 1.83
1.22;
0.69 - 2.17
1.36;
0.78 - 2.36
1.39;
0.71 - 2.61
<60,000 473 (21.8%) 1.00 1.00 1.00 1.00
60,000 - 75,000 533 (24.6%) 0.73;
0.52 - 1.02
0.67;
0.46 - 0.98
1.07;
0.73 - 1.56
1.18;
0.77 - 1.81
75,000 - 90,000 573 (26.4%) 0.78;
0.56 - 1.09
0.79;
0.54 - 1.14
1.07;
0.73 - 1.56
1.15;
0.75 - 1.76
Household income,
quartiles—EURO
>90,000 590 (27.2%) 0.62;
0.44 - 0.88
0.62;
0.43 - 0.91
0.87;
0.59 - 1.28
0.94;
0.61 - 1.46
Gender Female 1180 (54.1%) 1.66;
1.36 - 2.02
1.76;
1.38 - 2.24
2.03;
1.63 - 2.53
2.37;
1.79 - 3.13
Reduction in sport 338 (15.5%) 1.97;
1.46 - 2.66 1.51; 1.09 - 2.11
Begun to smoke 386 (17.7%) 1.81;
1.36 - 2.42 1.25; 0.93 - 1.69
More TV and PC time 1435 (65.8%) 1.58;
1.23 - 2.02 1.09; 0.96 - 1.24
Less fruit and vegetables 1106 (33.7%) 1.36;
1.06 - 1.73 1.48; 1.12 - 1.94
Less wholegrain bread 535 (24.5%) 1.19;
0.91 - 1.55 1.47; 1.10 - 1.97
*Adjusted for parents’ educational level, household income, baseline self-rated health or depressive symptoms and gender, **Adjusted for parents’ educational
level, household income, baseline self-rated health or depressive symptoms, gender and life-style changes.
Danish adolescents from age 15 to 18 years. The risk of
reporting poorer SRH after 3 years was lower in house-
holds with higher income, whereas parental educational
level was not associated with the development in SRH or
depressive symptoms. Adolescents who had adjusted
certain life-style factors in a negative direction from the
age of 15 to 18 reported poorer SRH and more depres-
sive symptoms. These results are consistent with what
has been observed in other longitudinal studies of health
related lifestyle among adolescents [20,21].
Despite the relatively high average household income
in this region of Denmark adolescents from households
within the lowest quartile of incomes had a statistically
significant increased risk of reporting poorer SRH after
the three-year period. SRH is a measure of perception of
general health rather than a measure of “true health”, but
such a measure seems indeed impossible to pinpoint [22].
Explanations for the effect of household income on
health have been hypothesized as the direct effects of
material living conditions (absolute deprivation) as well
as to social comparisons and experiences of relative dep-
rivation. The results from a meta-analysis and several
other studies among adults suggest a moderate adverse
effect of income inequality on health, but the population
impact might be large [23,24]. A British study found that
low household income was associated with lower SRH
and a number of other indicators of poor health among
children aged 5 - 15 years [25].
The discrepancy in findings related to the two measure
of SES (household income and parents’ highest educa-
tion) emphasize that these are two different indicators of
social status emphasizing different aspects—material
versus cognitive dimensions of socioeconomic status
[18]. From our results it seems that material circum-
stances better predict developments in SRH compared to
parental educational level.
Developing more health-compromising habits from
age 15 to 18 years was consistently associated with re-

J. H. Andersen et al. / Open Journal of Preve ntive Medicine 3 (2013) 104-110 109
porting both poorer SRH and, to a lesser extent, more
depressive symptoms in this group of adolescents. Even
though the study was prospective there could be reverse
causation in that, for example, a reduction in sporting
activities could be due to developing poorer SRH and
more depressive symptoms in the 3-year period. We
tested for an association between changes in health-
compromising habits as the outcome variables using
SRH and depressive symptoms as explanatory variables,
and found several significant associations indicating that
causation was bidirectional. The protective effect of
positive health behaviour is in line with similar findings
suggested in previous cross sectional studies [16,26,27].
Health-compromising behaviors and a lack of sporting
activity and exercise were also found to be risk factors
for deterioration in SRH in the Young-Hunt-Study,
which benefits from a 4-year observation period [4]. We
conclude that health risk behaviours, such as lack of lei-
sure time sporting activity and smoking may contribute
to later poor self-rated health. This has also been found
to be true over a follow-up period of 25 years [28]. But
in addition, developing more depressive symptoms and
experiencing a deterioration in SRH may also result in
health-compromising behaviours. This study benefits
from using register-based information on parents educa-
tion and household income. Comparing non-responders
at baseline and dropouts in the follow-up period it can be
seen that there were more non-responders and dropouts
from households with low income and the least parental
educational. This selection would tend to bias the results
towards the null.
From a public health perspective, this study supports
the idea that increasing sporting activities and providing
better opportunities for healthy nutrition in schools will
improve chances for the successful prevention of the
development of poorer health among adolescents. A re-
cent Cochrane review [29] found that there is some evi-
dence of positive effects on lifestyle behaviors and
physical health status measures, and that ongoing physi-
cal activity promotion in schools is recommended.
The study also points to the importance of giving spe-
cial attention to adolescents who develop more depres-
sive symptoms or experience a deterioration in SRH: this
group may be at greater risk of developing a health com-
promising lifestyle to put their health at further risk.
This research received no specific grant from any
funding agency in the public, commercial, or not-for-
profit sectors.
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