© 2007 The Royal College of Psychiatrists
Impact and clinical significance of a preventive intervention for disruptive boys
15-year follow-up
Research Unit on Children’s Psychosocial Maladjustment, University of Montreal, Montreal, Quebec, Canada
Social, Genetic and Developmental Psychiatry Centre, King’s College London, Institute of Psychiatry, London, UK
Research Unit on Children’s Psychosocial Maladjustment, University of Montreal, Quebec, Canada
Correspondence: Rachel Boisjoli, Research Unit on Children’s Psychosocial Maladjustment, University of Montreal, 3050 Édouard-Montpetit Boulevard, Montreal, Quebec H3T 1J7, Canada. Email: rachel.boisjoli{at}umontreal.ca
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Background Many intervention programmes have attempted to reduce disruptive behaviour problems during early childhood to prevent maladjustment during adolescence and adulthood.
Aims To assess the long-term impact and clinical significance of a 2-year multicomponent preventive intervention on criminal behaviour and academic achievement, using intention-to-treat analyses.
Method Targeted disruptive–aggressive boys considered to be at risk of later criminality and low school achievement (n=250), identified from a community sample (n=895), were randomly allocated to an intervention or a control group. The rest of the sample (n=645) served as the low-risk group. The intervention was multimodal and aimed at boys, parents and teachers. Official data measured both outcomes.
Results Significantly more boys in the intervention group (13%; P<0.05) completed high-school graduation and generally fewer (11%; P=0.06) had a criminal record compared with those allocated to the control group.
Conclusions The results suggest that early preventive intervention for those at high risk of antisocial behaviour is likely to benefit both the individuals concerned and society.
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Disruptive behaviour problems (aggressive, hyperactive and oppositional behaviours) during early childhood predict maladjustment (e.g. violence, criminality and school drop-out) during adolescence and adulthood (Farrington, 1992; Tremblay et al, 1992a; Moffitt, 1993; Patterson, 1996; Fergusson et al, 2002; Loeber et al, 2002; Vitaro et al, 2005). Intervention programmes have attempted to reduce disruptive behaviours to prevent such negative outcomes (e.g. Durlak & Wells, 1997; Farrington & Welsh, 2003). However, their long-term effects are rarely evaluated. Moreover, a significant long-term effect is not sufficient for claiming the efficacy of an intervention; its clinical significance has to be assessed by comparing its effects with a normative or low-risk group.
This study’s main objective was to evaluate whether participation in a preventive intervention targeting early disruptiveness predicted a higher rate of high-school graduation and a lower rate of crime involvement compared with the control group, by age 24 years. The second objective was to verify whether the boys who received the intervention would resemble the boys in the low-risk group with regard to the outcomes, whereas the boys in the control group would not.
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The global objective of the Montreal Longitudinal Experimental Study (Tremblay et al, 1992b) was to examine prospectively the development of a large sample of boys attending inner-city kindergartens who had backgrounds of low socio-economic status, with a particular focus on antisocial behaviour and school adjustment. Behaviour ratings of male pupils, mean age 6.1 years (s.d.=0.32), were obtained from 87% of the kindergarten teachers in 53 schools in areas of low socio-economic status in Montreal, Canada, at the end of the 1984 school year. A total of 1161 boys were rated. After exclusion of pupils who did not meet additional selection criteria – i.e. ethnicity (only boys with Canadian-born parents whose first language was French were included) and education (only boys whose parents had 14 years or less of schooling were included) – that number was reduced to 895. The purpose of these additional selection criteria was to create a homogeneous sample (through methodological control).
Boys were assessed by their kindergarten teacher by means of the Social
Behavior Questionnaire (SBQ; Tremblay
et al, 1991). This contains 38 items grouped into four
components: disruptive (13 items), anxious (5 items), inattentive (4 items)
and prosocial (10 items). The disruptiveness scale (
=0.93) includes
three categories of behaviour (Loeber
et al, 1989): aggression (3 items), oppositional
behaviour (5 items) and hyperactivity (2 items), and was used to identify
at-risk children. From the total sample, boys with a score above the 70th
percentile (n=250) on the disruptiveness scale were considered to be
at risk of later antisocial behaviour and dropping out of school
(White et al, 1990;
Tremblay et al,
1992a). Although this cut-off point is somewhat
arbitrary, it has been used successfully to predict serious maladjustment in
this sample (Tremblay et al,
1994). These 250 boys were randomly assigned to one of three
groups (prevention, n=69; attention–control, n=123;
control, n=58) by drawing the names from a box until the necessary
numbers were obtained. Given that no difference was found between the two
control groups on any outcome during adolescence or early adulthood (see
below), they were combined into a single control group for later analyses
(Fig. 1). The
attention–control group was equivalent to a no-treatment sensitisation
or contact control group; the control group was a no-treatment, no-contact
control group.
 View larger version (19K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Study profile.
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Preventive intervention programme
Three foci of the applied preventive intervention programme were based on a
literature review addressing early intervention with aggressive children
before 1984. The first theme identified was social skills training for the
disruptive boys (Cartledge & Milburn,
1980; Kettlewell & Kausch,
1983; Michelson et
al, 1983; Schneider &
Bryne, 1987). Social skills training aimed at promoting changes in
behaviour towards peers, yielding more social acceptance and less inclination
towards antisocial peers. Training was offered at school in small groups of
four to seven children, with a ratio of three prosocial children from the
school to one disruptive child in each group. The second focus was that of
parent training in effective child-rearing, based on the Oregon Social
Learning Center Model (Patterson et
al, 1975). The third domain was the provision of information
and support for teachers concerning at-risk boys, which served as a complement
to the parent training.
The intervention programme lasted 2 school years, from September 1985 to June 1987. Boys were 7 years old when the intervention started and 9 years old when it ended. A detailed description of the treatment is presented elsewhere (Tremblay et al, 1992b).
Implementation assessment
In order to evaluate programme exposure, the therapist responsible for each
child–family–teacher unit indicated at the end of each planned
training session whether or not the session had taken place and the percentage
of content that had been delivered in the session with regard to the
pre-planned, standardised content. Over 85% of the children who participated
in the intervention attended at least two-thirds of the social skills training
sessions. The maximum number of sessions given to the parents was 46, with the
mean number of sessions for the duration of the programme being 17.4,
including parents who discontinued their participation in the programme.
Parents were given as many sessions as needed to master the skills, following
the adaptive preventive intervention approach proposed by Collins et
al (2004). However, 75% of
the parents covered at least two-thirds of the content and objectives of the
planned training programme. Teachers demonstrated low interest and limited
availability; they were generally not able to spend much time discussing
teaching strategies for one child. Therefore, meetings with teachers were
fewer than planned (about 50% of teachers participated in at least one
meeting). Work with the parents and teachers was carried out by full-time
trained therapists: two university-trained childcare workers, one psychologist
and one social worker. Social skills training sessions were taped and used for
weekly feedback and to maintain the integrity of the programme across
therapists.
Control and outcome measures
Control variables assessed in kindergarten
Although no significant difference was found between the intervention group
and the control group after random assignment, two control variables –
parental occupational prestige and children’s disruptiveness –
were included in the analyses to completely level initial differences and
reduce bias in estimating the impact of the intervention programme. Parental
prestige was established using fathers’ and mothers’ occupational
status at pre-test and used as an indicator of family background. It was
calculated using the Canadian socio-economic status index of Blishen et
al (1987). This variable
is known to be linked to behaviour problems and delinquency and to high-school
graduation (Huesmann et al,
1984). The children’s disruptiveness variable used for
selection and pre-test was also used as a control variable.
Outcome measures collected at age 24 years
A high-school diploma was selected as the measure of scholarly achievement.
This variable was used instead of school drop-out or non-age-appropriate
regular classroom placement, previously used to assess school performance
(Vitaro et al, 2001),
because it represents a more definite measure; some boys who dropped out of
high school returned to complete their education and received a diploma. The
Ministry of Education of Quebec confirmed the award of a high-school diploma
as of year 2003 for 879 persons in the original sample, including 242 of the
original 250 participants in the prevention or control groups. This
categorical variable provided information on whether or not the participants
had obtained a high-school diploma by age 24 years. Overall, 427 of the 879
participants (48.6%) had done so.
Possession of a criminal record was selected as the measure of crime involvement. Criminal records were obtained from official files as of year 2003 for all of the 895 persons in the original sample, including the 250 participants in the prevention or control groups. This categorical variable provided information on whether or not the participant had a criminal record by age 24 years. Of the 895 participants, 178 (19.9%) had acquired a criminal record by age 24 years. Criminal offences were divided into five categories, as defined by the Ministry of Public Security of the Province of Quebec (prevalence for each category is shown in parentheses): crimes against persons, e.g. homicide (17.9%); property crimes, e.g. arson (31.2%); other Criminal Code offences, e.g. prostitution (25.5%); motor vehicle-related offences, e.g. impaired driving (8.8%); and drugs and narcotics-related offences, e.g. possession (16.4%).
Analyses
Two sets of analyses were performed, after verifying that the data did not
violate any of the assumptions of logistic regression. For the first set of
logistic regressions, achieving a high-school diploma and presence of a
criminal record were separately regressed on the experimental conditions (i.e.
intervention v. control) while controlling for parental occupational
status and disruptiveness. For the second set of logistic regressions, the
same outcomes were regressed on group membership (i.e. intervention and
control groups, plus the low-risk group) while controlling for parental
occupational status. In order to test the effectiveness of the programme, all
participants in the intervention sample were included in the
intention-to-treat analytic strategy, whether they received the intervention
or not.
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Differences between control and intervention groups
Frequencies of high-school graduation and criminal records are presented in Table 1.
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View this table: [in a new window] | Table 1 Frequencies of official record measures at age 24 years for the three study groups |
High-school graduation
After controlling for parental occupational status and initial level of
children’s disruptiveness, we found that being in the intervention group
was associated with a higher rate of high-school graduation than being in the
control group (ß=0.78, OR= 2.19, Wald 
2=6.06;
P<0.05).
Criminal record
Being in the intervention group was marginally associated with a lower rate
of criminal record than being in the control group (ß=–0.65,
OR=0.52, Wald 2= 3.68; P=0.06).
Differences between experimental groups and the low-risk group
High-school graduation
After controlling for parental occupational status, being in the
intervention group compared with being in the low-risk group predicted a
similar rate of high-school graduation (ß=–0.19, OR=0.83, Wald
2=0.52; NS), but being in the control group compared with
being in the low-risk group predicted a lower rate of high-school graduation
(ß=–0.84, OR=0.43, Wald 2=20.77;
P<0.0001).
Criminal record
Being in the intervention group compared with being in the low-risk group
predicted a similar rate of criminal record (ß=0.30; OR=1.35, Wald
2=0.92; NS), whereas being in the control group compared with
being in the low-risk group predicted a higher rate of criminal record
(ß=0.89, OR=2.45, Wald 2=21.69;
P<0.0001).
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The first goal of our study was to use intention-to-treat analyses to assess the long-term impact of a multicomponent preventive intervention programme targeting disruptive boys from homes with low socio-economic status; these boys were considered at high risk of low academic achievement and chronic antisocial behaviour. The impact of the programme was evaluated by contrasting disruptive boys who participated in the preventive programme and their counterparts in a control group on two outcomes: high-school graduation by age 24 years and official criminal records. The second goal was to compare the intervention group and the control group with the rest of the boys in the low socio-economic status group who initially scored below the 70th percentile on disruptiveness (i.e. the low-risk group).
Impact and social significance of the programme
As predicted, a positive effect of the intervention programme was found for
high-school graduation. The likelihood of having a high-school diploma was
more than twice as high for the intervention group as for the control group.
These results support earlier findings during adolescence on school drop-out
(Vitaro et al, 1999).
Although marginal, a positive effect of the intervention was also found for
possession of a criminal record: the likelihood of having a criminal record
was almost twice as high for the control group as for the intervention
group.
Comparing the experimental groups with a low-risk group on high-school graduation allows evaluation of the clinical significance of the intervention. In addition to the significant effect of the intervention on high-school graduation when compared with the control group, being in the intervention group predicted a rate of high-school graduation similar to that of the low-risk group. In the same way, the intervention group obtained a similar rate of criminal record as the low-risk group, whereas the risk of having a criminal record in the control group was more than double that for the low-risk group. These results confirm the relevance of reducing early disruptiveness to prevent later adjustment problems, and highlights the predictive power of early disruptiveness in an experimental clinical context.
Considering that, in adolescence, a significantly greater percentage of boys in the prevention group remained in an age-appropriate regular classroom compared with controls (Vitaro et al, 1999), and that the level of delinquency was higher for the control group compared with the intervention group (Lacourse et al, 2002), these results are not surprising. However, although encouraging, these findings should be considered in light of the fact that the rate of high-school graduation for the intervention group was only 46%, and the rate of having a criminal record was as high as 22%. In comparison, the rate of high-school graduation in the low-risk group was also low (68%) and the rate for criminal record was also high (16%), bringing the rates for the whole sample to 49% for high-school graduation and 19% for possessing a criminal record. In consequence, although boys in the intervention group became similar to their low-risk peers with respect to high-school graduation and criminal activities, the burden of other risk factors (i.e. low socio-economic status, inner-city residence) took its toll on the whole sample. It is thus important to acknowledge that a preventive intervention programme, albeit intensive, multimodal and long-term, has only a limited protective effect under the conditions of chronic socio-familial adversity and environmental risk.
Limitations
A number of limitations have to be considered. First, this study used only
one measure of antisocial behaviour. Official records used in this study can
be considered as a good indicator of antisocial behaviour, but their
interpretation is limited since they provide no direct information on
observable behaviours. On the other hand, the use of this measure resulted in
low attrition. It is also convenient for cost-effectiveness and clinical
significance analyses. Second, the sample was restricted to French-speaking
male participants of low socio-economic status. Generalisability is therefore
limited. A similar intervention with a mixed sample from a middle-class
environment could generate different results and yield different conclusions.
Finally, potential moderators and mediators still have to be explored.
Implications of the study
Despite these limitations, our study contributes to the critical need for
long-term follow-up investigations by giving a valuable and rare picture of
the long-term effects of an early preventive programme. This research also
allowed the clinical significance of the programme to be tested by comparing
the intervention and the control groups with a group of peers from the same
high-risk environment. Given the cost to society of criminality and failure to
graduate from high school (Kerckhoff &
Bell, 1998), this study also stresses the cost-effectiveness of
preventive intervention even if no formal examination of cost-effectiveness
was performed.
Taking into account these results, some considerations can be put forward. As suggested by Tremblay et al (1996), a longer intervention or a booster programme covering the transition to high school and into adulthood might have resulted in more robust effects during adulthood. In other words, the duration of the intervention (2 years) may not be sufficient or optimal, particularly when the external conditions are unfavourable. Several authors (Reid, 1993; Lochman & Wells, 1996) have suggested that an intervention should last for at least the whole elementary schooling period. As for the number of components, most experts agree on the importance of targeting different systems in children’s life, such as parents, teachers and the children themselves, as in the present study. However, additional systems such as peer groups should be targeted in future studies, in order to modify the additional important sources of influence that affect the development of antisocial behaviour (Coie & Jacobs, 1993; Greenberg et al, 2001; Boivin et al, 2005). Improving external conditions would also represent a good course of action for improving the impact of a child, family and school-centred preventive intervention.
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This research was supported by the Social Sciences and Humanities Research Council of Canada (grant 752-2005-1882).
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