Study
Tremblay and colleagues (1995) employed a longitudinal, randomized design to test the efficacy of the Preventive Treatment Program. In 1984, as part of the Montreal Longitudinal Study, teachers in 53 Montreal, Quebec schools with the lowest socioeconomic status index assessed all kindergarten boys in their classes (n = 1,161). The general aim of the study was to prospectively examine the development of a large sample of inner-city kindergarten boys, with a particular focus on antisocial behavior. From this sample, a subgroup of boys identified as disruptive in kindergarten was selected to test the effects of the Preventive Intervention Program.
Boys who were rated above the 70th percentile on the disruptive scale of the Social Behavior Questionnaire (n = 366) were considered to be at risk for later antisocial behavior. Of these boys, 319 were randomly assigned to a treatment group (n = 96), a control group (n = 71), or an attention-placebo control group (n = 152). Because of the refusal of some subjects to participate in the study, data was analyzed on 166 boys, including 43 in the treatment group, 41 in the control group, and 82 in the attention-placebo control group. However, because there were no between-group differences between the attention-placebo control group and the control group on any of the measures of interest, the two conditions were combined to form a single comparison group.
The treatment group received the preventive intervention that was administered to the boys and their parents when the boys were 7 years old and lasted until they turned 9. The attention-placebo control group boys participated in an intensive (school based, home based, and laboratory based) observational study. Every second year the families were visited during four evenings. Families also came to the university laboratory for a 3-hour session on a Saturday. The child was observed for a half-day at school on four occasions and spent a whole day in the university laboratory during the summer. The control group boys did not receive an intervention.
The three groups of disruptive boys were compared with a population-based random sample of kindergarten boys from French public schools in the Canadian province of Quebec in 1986–87 (n = 1,000). Families participating in the study were significantly more likely to be socioeconomically disadvantaged than the representative sample of their same-sex peers. In addition, parents of the disruptive boys in the study were consistently younger at the birth of their sons, and the total family income was lower.
The total sample of boys was assessed annually from age 10 (1 year after the end of the intervention), with the most recent analyses occurring when the boys were 15 (6 years after the end of the intervention). The outcome measures of interest included school adjustment, disruptive behavior, delinquency, and parenting behavior. School adjustment was measured by examining whether boys were placed out of a regular classroom appropriate for their age. At age 10 the boys should have been in a regular fourth grade class, and by age 15 they should have been in their third year of high school. Disruptive behavior was measured using teachers’ ratings on the Social Behavior Questionnaire. From ages 10 to 12, boys had one main elementary school teacher for the day. From ages 13 to 15, most boys had more than one teacher every day, so math and French teachers were used as raters because they had the most contact with the boys. For self-reported delinquency, boys completed a questionnaire addressing their involvement in antisocial behavior from ages 10 to 15. Eleven questions asked about theft, three questions asked about alcohol and drug use, and six questions asked about vandalism. At age 10, the boys were asked to report if they had ever misbehaved in the specified ways. From age 11, they were asked whether they had engaged in such behaviors in the previous 12 months. In addition to the questionnaire, juvenile court records were used to identify boys who had been placed under the Juvenile Offenders’ Act from ages 12 to 15 (this Canadian law does not apply before age 12). Youths are placed under this act if they are arrested by the police, charged, and found guilty of having broken a Canadian law. As such, they are officially designated as “delinquents.” Finally, parenting was assessed on the basis of boys’ perceptions of their parents’ childrearing practices, with questions specifically probing parental supervision and punishment during the previous 12 months.
To understand the effects of the treatment intervention from a development perspective, a repeated-measures approach was used to analyze the data. The study authors did not conduct subgroup analyses.
Study
Boisjoli and colleagues (2007) conducted a 15-year follow-up of the sample of boys from Study 1 (Tremblay et al. 1995). The main objective of the study was to examine whether boys who participated in the Preventive Treatment Program had higher rates of high-school graduation and lower rates of crime involvement compared with boys in the control group by age 24.
Data on whether participants had obtained their high school diploma by age 24 (as of 2003) was collected from the Ministry of Education of Quebec for 98 percent of the original study sample. Data on whether participants had criminal records by age 24 (as of 2003) was collected from official records for all participants from the original study sample.
Two sets of logistic regression analyses were conducted using the follow-up data. To test the effectiveness of the program, all participants in the treatment sample were included in the intention-to-treat analytic strategy, whether they received the intervention or not. The study authors conducted subgroup analyses on risk level.
Study
Vitaro and colleagues (2013) conducted a 19-year follow-up of the sample of boys from Study 1 (Tremblay et al. 1995) and Study 2 (Boisjoli et al. 2007). The goal of this study was to assess the impact of the Preventive Treatment Program on self-reported violent behaviors through age 28 using an intent-to treat (ITT) analysis. The violent behaviors measured were violence against persons (i.e., personal violence) and violence against property (i.e., property violence, including theft and vandalism).
Personal and property violence were measured using a 24-item Self-Report Delinquency Questionnaire (SRDQ; LeBlanc and Tremblay 1988), which assessed involvement in personal and property violence over the last 12 months.
Outcomes were examined at multiple points over three developmental periods: early adolescence (11–13 years old), mid-adolescence (14–16 years old), and late adolescence/early adulthood (17, 23, and 28 years old). The study authors did not conduct subgroup analyses.