timing and chronicity of family poverty and development of unhealthy behaviors in children: a...
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Journal of Adolescent Health 46 (2010) 538–544
Original article
Timing and Chronicity of Family Poverty and Development of Unhealthy
Behaviors in Children: A Longitudinal Study
Jake M. Najman, Ph.D.a,b,*, Alexandra Clavarino, Ph.D.c, Tara R. McGee, Ph.D.d,William Bor, M.B.B.S., D.P.M.e, Gail M. Williams, M.Sc., Ph.D., M.Sc., B.Sc.a,
and Mohammad R. Hayatbakhsh, M.D., Ph.D.a
aSchool of Population Health, University of Queensland, Herston, Queensland, AustraliabSchool of Social Science, University of Queensland, St Lucia, Queensland, Australia
cSchool of Pharmacy, University of Queensland, St Lucia, Queensland, AustraliadSchool of Justice Studies, Queensland University of Technology, Kelvin Grove, Queensland, Australia
eMater Centre for Service Research in Mental Health, Mater Hospital, South Brisbane, Queensland, Australia
Manuscript received January 12, 2009; manuscript accepted December 1, 2009
Abstract Purpose: To examine the impact of the timing and duration of family experiences of poverty over the
*Address correspo
tion Health, University
4006, Australia.
E-mail address: j.n
1054-139X/$ – see fro
doi:10.1016/j.jadoheal
child/adolescent early life course on child aggressive/delinquent behavior and tobacco and alcohol
consumption.
Methods: Data were taken from a large scale population based birth cohort study with repeated
follow-ups until 21 years after the birth. Poverty was measured during the pregnancy, 6 months, 5
years, and 14 years after the birth. Aggressive/delinquent behavior was measured at 14- and
21-year follow-ups. Tobacco and alcohol consumption were measured at the 21-year follow-up.
Results: In multivariate analysis, family poverty experienced at the 14-year follow-up predicted persis-
tent aggressive/delinquent behavior as well as smoking and higher levels of alcohol consumption at the 21-
year follow-up. However, the strongest associations were for recurrent experiences of family poverty, with
the group that experienced repeated poverty (3–4 times) being more than twice more likely to be aggres-
sive/delinquent at both 14 and 21 years, and to drink more than one glass of alcohol per day at 21 years.
Conclusions: Repeated experiences of poverty in early childhood and adolescence are strongly asso-
ciated with a number of negative health-related behavior outcomes. Experience of poverty in the early
adolescence seems to be the most sensitive period for such exposure. � 2010 Society for Adolescent
Health and Medicine. All rights reserved.
Keywords: Poverty; Child; Behavior; Young adult
Children who behave in a delinquent and/or aggressive
manner have poor developmental outcomes, are more likely
to experience ongoing poor health throughout their lives, and
have an increased risk of premature death [1, 2]. Under-
standing why some young people become aggressive or
delinquent and others do not is an important public health
issue. Family poverty has been shown to have a strong rela-
tionship with a child’s aggressive/delinquent behavior and
ndence to: Jake M. Najman, Ph.D., School of Popula-
of Queensland, Herston Road, Herston, Queensland
nt matter � 2010 Society for Adolescent Health and Medic
th.2009.12.001
also high-risk behavior such as tobacco smoking and alcohol
use [3–7]. The causal process that produces this association
remains poorly understood. Little is known about how
changes in family economic status over the child’s/adoles-
cent’s life course affect child health and related behavior
[8]. This reflects a more general lack of knowledge regarding
the effect of timing and duration of exposure to poverty on
child behavior outcomes. One concern which has not been
adequately addressed is whether there is a ‘‘sensitive’’ period
when family experience of poverty disproportionately affects
child developmental outcome. If the timing or duration of
family poverty is strongly associated with delinquent and/
or aggressive behavior then this will have implications for
policy and practice.
ine. All rights reserved.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544 539
Timing and duration of exposure to povertyand aggressive/delinquent behavior
Little is known about the age at which family poverty has
the greatest impact on children, with both the childhood and
adolescent period being identified as most important in
different studies. A relationship between poverty and aggres-
sive/delinquent behavior has been observed from as early as 4
or 5 years of age [3–6]. In examining the timing of poverty in
the National Longitudinal Survey of Youth (NLSY), Jarjoura
et al. [9] found that living in a poor family during the first 5
years of life was related to an increased likelihood of delin-
quent behavior in adolescence. In addition, family poverty
measured at 11 years was also associated with increased
concurrent delinquency in children. This study suggests that
timing of poverty is important, with the most detrimental
timing for poverty being the first 5 years of life. In contrast,
the National Institute of Child Health and Human Develop-
ment [4] reports that children in the National Institute of Child
Health and Human Development Study of Early Child Care
and Youth Development, who experienced poverty from
age 4 to 8, report more externalizing behavior problems
than children who were poor in only the first 3 years of life.
It is important to note that the ‘‘early’’ and ‘‘late’’ exposure
groups in this study included only a narrow age range. In
contrast, timing of poverty (in a sample limited to very young
children) has not been found to influence 5-year-olds’ exter-
nalizing behaviors [10]. There are simply too few studies to
know whether timing of exposure to poverty influences
aggressive/delinquent and substance use behavior in children.
Duration of exposure to poverty may also be important for
later aggressive/delinquent behaviors. Examination of the
NLSY shows that persistent poverty (for 8 years in duration)
is associated with higher levels of delinquency than short-
term poverty [9]. Earlier analyses of the same data [11]
showed that children who were poor from age 4 or 5 years
until age 8 or 9 years had substantially higher rates of exter-
nalizing behaviors than did transiently poor or non-poor chil-
dren (after controlling for family history of poverty before
age 4/5). Bolger et al. [12] report that children in the Charlot-
tesville Longitudinal Study, who experienced persistent
poverty over a 4-year period (starting from ages 8 to 10 years)
were more likely to manifest conduct problems at school than
transiently poor children, who in turn were more likely to
have conduct problems than children who were never poor.
Overall, these studies are consistent with a review which
suggests that lengthy exposure to poverty is more detrimental
than transient poverty [8].
Other studies report findings that contradict the above
results. For example, Pagani et al. [13] examined the relation-
ship between poverty and extreme delinquency in boys from
the Montreal Experimental-Longitudinal Study and found
that the risk associated with persistent poverty (being poor
from age 10 to 15 years) did not exceed that of intermittent
poverty. McLeod and Shanahan [14] report that persistent
poverty does not predict externalizing symptoms above and
beyond the effects of current poverty in children aged 4–8
years in the NLSY. Finally, Dearing et al. [15] report that
4–5-year-old children in the Study of Early Child Care and
Youth Development exhibited higher levels of externalizing
behaviors during periods when family income was low, in
contrast to times when family income was relatively high.
These studies suggest that current income level is more
important than persistent poverty.
Overall, it is clear that poverty is related to aggressive and
delinquent behavior. However, the relative contribution of
timing (early vs. late childhood) and duration of poverty
requires further investigation. Whether poverty impacts
largely on those with early onset of aggressive/delinquent
and substance use behavior also remains to be determined.
To explore the association between poverty and child
behavior, there is also a need to take account of a number
of factors that may distort these association. Gender of the
child has previously been found to be associated with aggres-
sion, such that adolescent males exhibit more aggressive/
delinquent behaviors than females [16]. Previous investiga-
tions have also suggested that family backgrounds such as
mother’s age, marital status, education, and mental health
predict child’s behavioral problems and are associated with
poverty [8, 17, 18]. Therefore, associations of family poverty
and child behaviors should be corrected for these possible
confounding factors. Using data from an Australian prospec-
tive birth cohort, this study will investigate the effects of
timing and persistence of poverty on aggression/delinquency,
in participants aged 14 and 21 years, and on tobacco and
alcohol-use at age 21 years, and whether this association is
independent of possible confounding factors.
Methods
Participants
We used data from the Mater-University Study of Preg-
nancy, a prospective longitudinal study of a consecutive
cohort of individuals born in Brisbane, Australia, between
1981 and 1984 at a major public hospital (Mater Misericor-
diae Hospital). The hospital involved was one of only two
major obstetrical hospitals in Brisbane, and served the south
side of the city. Recruitment procedures for the larger study
have been detailed elsewhere [see 19]. The cohort consists
of 7,223 women (and their children) who agreed to partici-
pate, and delivered a live singleton infant who was not adop-
ted out. This represents 87% of all women who attended the
antenatal clinic during the study period. Mothers completed
questionnaires at their first antenatal clinic visit, 3–5 days
after birth, and 6 months and 5 years after birth. Both mother
and children completed questionnaires at 14 and 21 years
after birth. Participants (N¼ 3,103) were included if they
provided information on aggression/delinquency at 14 and
21 years and smoking and alcohol consumption at 21 years
and for whom data were available about measures of poverty
between the first clinic visit and child’s age 14 years.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544540
Response rates were maximized by using the following strat-
egies:
� At recruitment mothers were asked to provide about six
family/friends’ contact details so that if the respondent
had moved at follow-up, they could still be contacted.
� The electoral (voting) roll was searched for details of
any change of address. In Australia voting is compul-
sory and all persons over 18 years are required to
register.
� The telephone directory was searched for updated
contact details.
� Newspaper death notices were searched to locate
persons who were deceased.
� Where all other efforts had failed, an interviewer would
visit the previous address and ask neighbors if there was
a forwarding address.
There were very few refusals to participate. Most of the
loss to follow-up reflects the high mobility of the sample,
some of whom had moved to other states and overseas.
Ethical clearances were provided by the relevant commit-
tees at each stage of follow-up. Both the Mater Hospital and
The University of Queensland separately reviewed the
project at each data collection. Respondents were
approached, provided with details of the follow-up, and
were informed that participation was voluntary. Only those
who consented to participate were recruited to the study.
Up to the 14-year follow-up, mothers provided consent for
their own and their child’s participation. At the 21-year
follow-up, mothers and young adults were individually
invited to continue to participate in the study.
Measures
Family income
Mothers were asked about their total gross annual house-
hold income (including spouse’s income, child endowment,
etc.) during pregnancy (average¼ 18 weeks gestation),
when the child was 6 months, 5 years, and 14 years old. There
were seven discrete income categories as response options
(listed in weekly and annual amounts). At each phase family
income was classified into two categories with the 25 centile
being the cut-off for low income. This sample derives from
a public (free) hospital, which attracts a higher proportion
of low-income earners than there are in the population [20]
for details of sampling.
Child aggressive/delinquent behavior
Child aggressive/delinquent behavior was assessed from
their responses to the Youth Self Report (YSR) [21] version
of the Child Behaviour Checklist [22] at age 14 years and the
Young Adult Self Report (YASR) [23] at the 21-year follow-
up. The YSR and YASR are similar measures and have been
validated to provide standardized checklists of child behavior
problems and competencies [24]. Response alternatives in
our study were ‘‘often,’’ ‘‘sometimes,’’ or ‘‘rarely/never’’
rather than not true, sometimes true, often/very true, as was
used in the original scale. Factor analyses and reliability esti-
mates of subscales produced results consistent with Achen-
bach’s data [22, 25]. In the present study, both YSR and
YASR Aggressive/Delinquent scale had good internal reli-
abilities (Cronbach’s alpha: YSR¼ .92, YASR¼ .87).
Symptoms were totaled according to standard protocols.
Scores for the group in the top decile of aggressive/delin-
quent behavior were used to define the cut-off for ‘‘case-
ness.’’
Young adults’ smoking and alcohol consumption
The extent of child smoking and alcohol use at 21 years
was assessed via self-report. Based on their responses we
divided participants into three categories: nonsmokers,
smoking less than 10, and 10 or more cigarettes per day;
abstainers, drinking up to one glass, and more than one glass
of alcohol per day.
Other covariates
The distinction between a confounder and a mediator
depends on the aims/objectives of a study. This study has
a primary focus on the impact of family poverty on child
behavior. For example, if family poverty affects, say,
maternal mental health, and maternal mental health affects
child behavior, then this sequence may be considered causal
from the perspective taken by this study. It is for this reason
that most of the covariates are measured at the time the
mother was recruited to the study.
Two categories of variable were included as confounders
and/or mediators. For model 1 we adjusted for the respon-
dents’ sociodemographic and family characteristics
including child gender, maternal age, marital status, and
maternal and paternal education. For model 2 we added
a range of maternal mental illness and maternal and paternal
lifestyle variables to the previous adjustment.
Mother’s age, marital status, and maternal and paternal
education were assessed at first clinic visit. Marital status at
entry to the study was divided into two categories: mothers
who were married or living in a de facto relationship and
mothers with no partner (single, separated/divorced, or wid-
owed). Maternal anxiety and depression were assessed at
entry to the study using the Delusion-Symptoms-States
Inventory of anxiety and depression [26]. Maternal smoking
was also assessed at the first clinic visit as well as maternal or
paternal history of arrest at the 5-year follow-up.
Statistical analysis
Participants who provided information on aggressive/
delinquent behavior at 14 and 21 years, smoking and
drinking at 21 years, estimates of family income at each
phase, and information on maternal age, marital status,
maternal and paternal education, maternal smoking, maternal
Table 1
Exposure to poverty at different stages during development and child aggression/delinquency, smoking, and drinking at 21 years
Poverty status Aggression/delinquency at 14 and 21 years Smoking at 21 years (cigarettes per day) Drinking at 21 years (glasses per day)
Pregnancy N None % Either % Both % Nil % <10 % �10 % Nil % �1 % >1 %
Not poor 2,180 77.7 18.4 3.9 65.7 17.5 16.7 31.7 61.0 7.3
Poor 896 76.8 18.2 5.0 62.2 16.4 21.4a 35.3 56.4 8.4
6 mo
Not poor 2,308 78.1 18.2 3.7 66.1 17.3 16.6 31.1 61.6 7.4
Poor 675 75.6 18.1 6.4b 61.0 17.8 21.2b 36.7 55.0 8.3a
5 yr
Not poor 2,215 78.9 17.6 3.5 67.0 17.2 15.8 31.1 62.1 6.9
Poor 634 74.0 20.2 5.8a 59.3 17.4 23.3c 34.9 54.3 10.9c
14 yr
Not poor 2,569 78.3 17.6 4.0 65.4 17.1 17.4 32.2 61.0 6.8
Poor 591 73.3 21.2 5.6b 60.1 17.6 22.3b 35.2 54.3 10.5a
Note: statistically significant at the:a p < .01.b p < .05.c p < .001.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544 541
and paternal arrests, and maternal mental health were
included in the present analysis. We used chi-square tests
and logistic regression models to examine the association
between exposures to family poverty at different stages of
child development and child aggressive/delinquency,
smoking, and alcohol consumption. We then used logistic
regression models to estimate the association between
frequency of exposure to poverty and child outcomes
measured at 14 and 21 years. In multivariate analyses, we
successively adjusted for the family/child’s sociodemo-
graphic characteristics and mothers’ mental health and life-
style. All analyses were carried out using STATA v.10 and
SPSS v.15.
Results
Table 1 presents the association between family poverty
experienced by the individuals over the early life course
and aggressive/delinquent behavior, smoking, and alcohol
consumption at ages 14 and 21 years. Family poverty during
pregnancy is not associated with subsequent aggression/
delinquency and alcohol consumption; however, family
poverty in early and later childhood, and the adolescent
Table 2
Multivariate association between family poverty and child aggression/delinquency
Aggression/delinquency at 14 and 21 years Smoking at
OR (95% CI)b OR (95% C
Timing of poverty Either Both <10
Pregnancy 1.0 (0.8–1.3) 1.2 (0.7–1.9) 1.0 (0.8–1.2
6 mo 1.0 (0.7–1.3) 1.4 (0.8–2.2) 1.2 (0.9–1.6
5 yr 1.2 (0.9–1.5) 1.5 (0.9–2.4) 1.0 (0.7–1.3
14 yr 1.3 (1.0–1.7) 1.6 (1.0–2.5) 1.1 (0.8–1.5
a Adjusted for poverty at other phases.b Neither 14 nor 21 years reference category.c Nonsmoking reference category.d Nondrinking reference category.
period are all associated with aggression/delinquency.
Smoking and alcohol consumption at 21 years are also asso-
ciated with early life course experiences of family poverty at
6 months, 5 years, and 14 years.
The independent effects of poverty over the early life
course are considered in Table 2. The reference categories
are no aggression/delinquency, no smoking, and drinking
less than a glass of alcohol a day on average. Only family
poverty at the 14-year follow-up independently predicts
aggression/delinquency at either the 14- or 21-year, or both
follow-ups. Family poverty at the 5- and 14-year follow-
ups independently predicts smoking at 14- and 21-year
follow-ups, with a similar finding for alcohol consumption
averaging one or more glasses a day at the 21-year follow-
up. However, while these associations are statistically signif-
icant, the point estimates of the magnitude of effect are
moderate.
While the experience of family poverty at particular stages
of the early life course predicts aggression/delinquency,
smoking, and alcohol consumption, it is repeated experiences
of family poverty that provides the strongest prediction of
‘‘negative’’ behavioral developmental outcomes (Table 3).
Negative behavioral outcomes are most evident for those
, smoking, and drinking at 21 yearsa
21 years (cigarettes per day) Drinking at 21 years (glasses per day)
I)c OR (95% CI)d
�10 �1 >1
) 1.2 (1.0–1.6) 1.1 (0.9–1.3) 1.1 (0.8–1.6)
) 1.1 (0.8–1.4) 1.1 (0.9–1.4) 0.9 (0.5–1.2)
) 1.4 (1.1–1.9) 1.2 (1.0–1.5) 1.7 (1.2–2.4)
) 1.3 (1.0–1.7) 1.0 (0.8–1.3) 1.5 (1.0–2.2)
Table 3
Number of exposures to poverty over first 14 years of life and child aggression/delinquency at 14 and 21 years adjusted for other covariates
Unadjusted Adjusted (Model 1) Adjusted (Model 2)
OR (95% CI)a OR (95% CI)b OR (95% CI)c
Exposure to poverty N Either Both Either Both Either Both
Never poor 1,520 1.0 1.0 1.0 1.0 1.0 1.0
Poor once 817 1.1 (0.9–1.4) 1.4 (0.9–2.1) 1.1 (0.9–1.4) 1.3 (0.8–2.1) 1.1 (0.9–1.4) 1.2 (0.7–2.0)
Poor twice 467 1.0 (0.7–1.3) 1.4 (0.9–2.4) 0.9 (0.7–1.2) 1.2 (0.7–2.0) 0.9 (0.7–1.2) 1.3 (0.7–2.4)
Poor 3–4 times 299 1.3 (0.9–1.8) 2.6 (1.5–4.3) 1.1 (0.8–1.5) 2.0 (1.1–3.5) 1.0 (0.7–1.5) 2.0 (1.1–3.6)
a Neither 14 nor 21 years reference category.b Model 1 adjusted for child gender, maternal age, maternal marital status, maternal education and paternal education at first clinic visit.c Model 2 adjusted for Model 1 plus maternal anxiety and depression and maternal smoking at first clinic visit, maternal and paternal arrest within first 5 years
after the birth.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544542
respondents who met the criteria for aggressive/delinquent
behavior at both the 14- and 21-year follow-ups (those man-
ifesting more chronic persistent aggressive/delinquent
behavior). After adjustment for other family sociodemo-
graphic (model 1) and family lifestyle (model 2) variables
the association is somewhat attenuated but remains strong
(point estimate).
Table 4 presents the association between repeated experi-
ences of family poverty over the early life course and ciga-
rette smoking at the 21-year follow-up. While early life
course experiences of poverty predict smoking in young
adulthood, this association is reduced once there is further
adjustment for family lifestyle (model 2). It appears that it
is not poverty alone but family characteristics such as educa-
tion and maternal smoking that lead to young adult smoking.
Table 5 examines early life course exposure to poverty
and young adult alcohol consumption. The associations are
strong and consistent. Repeated experiences of family
poverty over the early life course are associated with higher
rates of alcohol consumption by young adults.
This remains the case after adjustment for the sociodemo-
graphic characteristics of the family (model 1) and the life-
style of the family (model 2).
Discussion
The large body of evidence which has established that
family poverty is associated with aggressive/delinquent and
Table 4
Number of exposures to poverty over first 14 years of life and smoking (cigarettes
Unadjusted
OR (95% CI)a
Exposure to poverty N <10 �10
Never poor 1,520 1.0 1.0
Poor once 817 1.0 (0.8–1.3) 1.5 (1.2–1.9)
Poor twice 467 1.0 (0.8–1.4) 1.5 (1.1–1.9)
Poor 3–4 times 299 1.1 (0.8–1.5) 1.9 (1.4–2.6)
a Non-smoking reference category.b Model 1 adjusted for child gender, maternal age, maternal marital status, matec Model 2 adjusted for Model 1 plus maternal anxiety and depression and matern
after the birth.
substance using behaviors over the child’s early life course
raises some important questions. One concern is the impact
of poverty during specific stages of the life course. For
example, does poverty in early childhood make a specific
contribution to child behavior problems, or is it the adoles-
cent period that is more important? Of course, this needs to
be distinguished from the duration of time a child lives in
poverty and from the possible influence of other factors asso-
ciated with the family life of children living in poverty.
Our findings first examine the impact of timing of poverty
on adolescent/young adult aggressive/delinquent behavior.
Although family poverty at a number of different stages of
the child’s early life are associated with recurrent aggres-
sive/delinquent behavior, the adjusted comparisons suggest
that family poverty experienced during the adolescent period
has the strongest and most consistent independent association
with aggressive/delinquent behavior. Heavier levels of
smoking and alcohol use are associated independently with
poverty in childhood (5-year follow-up) as well as in adoles-
cence (14-year follow-up). However, while our findings
suggest that the adolescent period is the most sensitive
(consistent effect) for the impact of family poverty on child
aggressive/delinquent behavior, smoking, and alcohol
consumption, the associations are not very strong.
On the other hand, repeated experiences of family poverty
during the early life course strongly predict persistent aggres-
sive/delinquent behavior, alcohol consumption at age 21
years and, to a lesser extent, smoking at age 21 years. After
per day) at 21 years adjusted for other covariates
Adjusted (Model 1) Adjusted (Model 2)
OR (95% CI)b OR (95% CI)c
<10 �10 <10 �10
1.0 1.0 1.0 1.0
1.0 (0.8–1.3) 1.1 (1.1–1.7) 1.0 (0.8–1.3) 1.3 (1.0–1.7)
0.9 (0.7–1.2) 1.1 (0.8–1.5) 0.9 (0.7–1.3) 1.1 (0.8–1.5)
0.9 (0.6–1.3) 1.4 (1.0–1.9) 0.9 (0.6–1.3) 1.3 (0.9–1.8)
rnal education ,and paternal education at first clinic visit.
al smoking at first clinic visit, maternal and paternal arrest within first 5 years
Table 5
Number of exposures to poverty over first 14 years of life and alcohol consumption (glasses per day) at 21 years adjusted for other covariates
Unadjusted Adjusted (Model 1) Adjusted (Model 2)
OR (95% CI)a OR (95% CI)b OR (95% CI)c
Exposure to poverty N �1 >1 <10 �10 �1 >1
Never poor 1,520 1.0 1.0 1.0 1.0 1.0 1.0
Poor once 817 1.2 (1.0–1.5) 1.1 (0.8–1.6) 1.2 (1.0–1.5) 1.2 (0.8–1.7) 1.3 (1.1–1.6) 1.1 (0.7–1.6)
Poor twice 467 1.2 (1.0–1.5) 1.3 (0.9–1.9) 1.1 (0.9–1.4) 1.3 (0.9–2.0) 1.1 (0.8–1.4) 1.2 (0.8–2.0)
Poor 3–4 times 299 1.6 (1.2–2.1) 2.4 (1.6–3.7) 1.5 (1.1–2.0) 2.7 (1.7–4.1) 1.6 (1.2–2.2) 2.6 (1.6–4.3)
a Nondrinking reference category.b Model 1 adjusted for child gender, maternal age, maternal marital status, maternal education, and paternal education at first clinic visit.c Model 2 adjusted for Model 1 plus maternal anxiety and depression and maternal smoking at first clinic visit, maternal and paternal arrest within first 5 years
after the birth.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544 543
adjustment for family sociodemographic characteristics the
strong impact of repeated experiences of poverty over the
early life course remain for aggressive/delinquent and higher
levels of alcohol use behavior. This remains the case after
adjustment for family lifestyle variables. Our findings
suggest that family poverty has an effect on adolescent/young
adult health related behavior, which is independent of the
level of education the family has achieved, and many other
indicators of social disadvantage (young maternal age, non-
married status, family contact with criminal justice system).
There appears to be an aspect of living in poverty that is
damaging to the developmental health of the child above
many of the cultural and material elements that are likely to
be reflected by such variables as education, marital status,
and family lifestyle. It may be that children who experience
chronic family poverty over longer periods of their early
life course ‘‘give up’’ seeking to join mainstream of society,
the middle class majority. For these children social networks
may become restricted to like-behaving peers; and the
priority given to living a healthy, nonviolent lifestyle dimin-
ishes as their social exclusion becomes a more evident feature
of their day-to-day lives.
It is particularly important to reflect on our findings, which
suggest that repeated experiences of family poverty in child-
hood lead to high rates of aggressive/delinquent behavior. If
our findings are correct then both treatment and broader
policy responses need to be considered. While tobacco
smoking and high levels of alcohol consumption are matters
of concern, they are also likely to be indicative of the devel-
opmental origins of a wide range of unhealthy behaviors.
From a policy perspective our findings point to, first, the
need to reduce the period of time a child lives in family
poverty and, second, to develop programs that target a broad
range of behavioral problems at or around the adolescent
period. Others have noted the substantial increase in aggres-
sive/delinquent behavior that occurs for both males and
females coincident with the onset of puberty [27]. Early
childhood intervention to reduce levels of aggressive/delin-
quent behavior may miss the point in the life course when
this aggressive/delinquent behavior increases, and when
programs have relevance to those involved.
Our findings suggest that children repeatedly experi-
encing poverty during their early life course may manifest
persistent behavioral problems, possibly because they no
longer share the values and beliefs of the middle class,
affluent society from which they are effectively excluded.
Whatever the value and belief consequences of poverty
may be, these may need to be addressed if programs are
to be successful.
Limitations
There are a number of limitations of this study, which are
relevant to interpreting our findings. Loss to follow-up was
substantial and nonrandom. As we have noted elsewhere,
[19] those who are economically disadvantaged and with
poorer mental health, are more likely to be lost to follow-
up. We have undertaken extensive statistical modeling using
a variety of methods of imputation to assess the likely effects
of attrition [19]. Considering both the differential levels of
follow-up characteristics of different socioeconomic groups,
and the magnitude of the associations we observe, it appears
that loss to follow-up (in our study there are higher rates of
attrition for children who live in poverty and who report
aggressive/delinquent behavior), leads to slightly conserva-
tive estimates of the findings we would obtain without bias
in attrition. We have undertaken extensive statistical
modeling of the effects of loss to follow-up, using various
best and worst case scenarios (in effect these are sensitivity
analyses). The results of these are consistent in suggesting
that our findings are likely to be modest underestimates of
the true association had we not had loss to follow-up.
A second limitation involves our measures of aggressive/
delinquent behavior. While we infer chronicity of aggressive/
delinquent behavior when adolescents/young adults meet the
10% cut-off on two occasions, this is an imperfect inference.
The study would have been stronger had we measured
aggressive/delinquent behavior more frequently, and had
we had available a broader range of indicators of aggres-
sive/delinquent behavior. Further, it would have been useful
to have more detail of the adolescents’ pattern of tobacco and
alcohol consumption.
J.M. Najman et al. / Journal of Adolescent Health 46 (2010) 538–544544
Conclusions
Early life course influences such as family poverty are
likely to initiate a lifestyle and health-related behaviors that
are maintained over the adult life course, and that have
numerous short-, medium-, and long-term consequences.
This includes not only aggressive/delinquent behaviors but
also behaviors associated with tobacco and alcohol consump-
tion, impaired mental health, and social relationships across
the adult life course. Persistent family poverty predicts the
onset and development of a range of behaviors, which lead
to negative health outcomes. The pathway from experiences
of persistent poverty, to a range of unhealthy behaviors in
young adulthood, and then premature poor health and death,
should be the focus of systemic policy responses.
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