In this article, we examine whether universal family-focused interventions conducted during sixth grade can reduce problematic substance use during young adulthood through their impact on adolescent substance initiation. Epidemiological data highlight how problematic or serious types of substance use often are more prevalent in young adulthood than in earlier developmental stages (Johnston, O'Malley, Bachman, & Schulenberg, 2007
; Substance Abuse and Mental Health Services Administration, 2007
). The consequences of problematic adult substance use include less competent functioning and lower educational and occupational attainment (Ackerman, Zuroff, & Moskowitz, 2000
), risky sexual practices (Park, Mulye, Adams, Brindis, & Irwin, 2007
), mental health problems (Windle & Windle, 2001
), adult crime (Kosterman, Graham, Hawkins, Catalano, & Herrenkohl, 2001
), and increased mortality (Park et al., 2007
Many of the risk and protective factors for adolescent substance misuse originate in the family environment (Hawkins, Catalano, & Miller, 1992
; Wood, Read, Mitchell, & Brand, 2004
). These include parental monitoring, consistent discipline, clear communication about rules and expectations, and parent–child affection and warmth. For this reason, family-focused preventive interventions designed to reduce substance use among elementary and middle school age children have been developed. Reviews of the literature on family-focused intervention reveal a number of effective strategies (see Alexander, Robbins, & Sexton, 2000
; Lochman & van den Steenhoven, 2002
; Spoth, 2008
; Spoth, Greenberg, & Turrisi, 2008
; Taylor & Biglan, 1998
) with a range of formats (e.g., DVD-based, group formats, reading materials with professional support provided via telephone calls), targeted populations (e.g., at-risk families, rural vs. urban), and intervention settings (e.g., home, school, community, health care). Among the promising strategies are community-based interventions offered to groups of general population families, frequently labeled universal programs.
A number of universal interventions have been shown to be effective in delaying substance initiation during the adolescent period (National Institute on Drug Abuse, 2003
; Spoth et al., 2008
); very few studies, however, have followed participants into young adulthood. A recent report demonstrated continued positive effects into young adulthood for a longer, more intensive, multi-component school and family-based preventive intervention on a range of outcomes (Hawkins, Kosterman, Catalano, Hill, & Abbott, 2005
; see also Poduska et al., 2008
). These positive effects of intensive intervention on long-range outcomes encourage investigating whether briefer
, universal family-focused
interventions also might produce long-lasting positive effects.
The extant literature on universal interventions emphasizes the importance of timing program implementation to occur during the developmental window when adolescents are just beginning to initiate substance use. Epidemiological research suggests that well-timed interventions could accrue substantial public health and economic benefits, should they delay onset of substance use or delay transition to more serious use (Anthony, 2003
; Chen et al., 2004
; Offord & Bennett, 2002
). Indeed, the interventions investigated in the current report have demonstrated favorable results in delaying adolescent substance initiation and reducing adolescent substance use (e.g., Spoth, Redmond, & Shin, 2001
; Spoth, Redmond, Shin, & Azevedo, 2004
). This pattern of earlier results sets the stage to address whether these comparatively proximal effects in adolescence portend continued favorable effects on problematic substance use in young adulthood.
Etiological research provides the rationale for hypothesizing that intervention effects delaying substance initiation will be related to reduced adult substance use. Research has demonstrated that substance-related risk factors that endure in adolescence predict problematic substance use in young adulthood (Guo, Hawkins, Hill, & Abbott, 2001
; Hawkins et al., 1997
; White et al., 2006
). Therefore, the observed intervention effects among adolescents should translate into less problematic use in young adulthood.
To address the gap in the literature pertaining to long-term effects of family-based universal interventions, in the current study we examined a developmental model of long-term effects of two such interventions implemented during early adolescence on young adult substance use outcomes 10 years after intervention implementation. From a developmental perspective, early adulthood is particularly important for evaluating intervention effects because it is the stage in which problematic use typically increases, and because it entails major changes in roles and responsibilities in home, work, and school environments that could be impacted by substance use (Schulenberg, Sameroff, & Cicchetti, 2004
The tested developmental model was designed to address a number of issues in the examination of long-term intervention outcomes. The first issue concerns the mechanisms of intervention-related change. Over the past 2 decades, leading program evaluators have recommended, in addition to analyses of direct intervention outcomes, testing models that examine sequences of intervention effects on substance use or mechanisms of intervention-related change (Lipsey, 1990
). However, the literature also clearly indicates it has been difficult to demonstrate indirect or mediating effects of interventions across developmental stages (Shrout & Bolger, 2002
). In addition to very limited research to date, only weak support has been found for hypothesized intervention mechanisms (Ennett et al., 2001
; Orlando, Ellickson, McCaffery, & Longshore, 2005
The second issue concerns the challenge of modeling the complex interplay of long-term intervention effects, age-related patterns of substance use, and developmental processes (Masten, Faden, Zucker, & Spear, 2008
; Masten et al., 2005
). Modeling intervention effects on substance initiation trajectories is a parsimonious way to capture intervention effects across a long developmental time span (see Blozis, Feldman, & Conger, 2007
). These trajectories can be viewed as the result of multiple interrelated pathways of intervention effects (e.g., proximal effects on early adolescent substance refusal skills, parental monitoring, and other vectors of influence) that may convey intervention effects into young adulthood. The developmental model examined herein posits that (a) the range of previously demonstrated proximal effects of the tested universal interventions (intervention-related effects on parenting, such as parental monitoring, along with effects on adolescents' intention to use, attitudes, or skills; e.g., Spoth, Redmond, & Shin, 1998
) likely delays substance initiation or slows its rate of increase across the adolescent years and decreases the average level of initiation (e.g., Spoth et al., 2001
), and (b) those effects on substance initiation are the primary means by which long-term effects into young adulthood are produced.
A third set of issues is methodological in nature. In the current study, we address several limitations of previous studies with regard to intervention effects across developmental stages. These limitations include (a) failure to account for time-related changes in initiation across adolescence, (b) reliance on retrospective reports of behaviors that occurred many years prior to data collection, and (c) focusing on urban samples, as compared with the rural sample in the present study (Hawkins et al., 2005
). The analytic method of the current study entails latent growth modeling that specifies proximal intervention effects on adolescents' average level and rate of increase of substance initiation, with effects on young adult substance outcomes modeled as more distal indirect effects, similar to analytic strategies used in relevant etiological research (e.g., Blozis et al., 2007
A final issue to address is the practical significance of small intervention effects observed at points well beyond intervention implementation. As detailed in the Method section, this is accomplished by performing an additional set of analyses in which the young adult outcome variables are dichotomized, on the basis of specified threshold values defining caseness for each outcome. Caseness is defined as a level of use that likely is problematic from a public health perspective. Comparison of the case rates in the intervention and control conditions yields relative reduction rates (RRRs), which correspond to the proportion of control condition cases that would have been prevented had those individuals been in the intervention condition.
Earlier work with this young adult data set evaluated the social development model-based mediators of Preparing for the Drug Free Years (PDFY), one of the currently tested interventions. The authors of that article applied regression and structural equation modeling to examine mechanisms of intervention effects on a single diagnostic outcome: alcohol abuse at 21 years of age (Mason et al., in press
). Consistent with literature indicating the difficulty of disentangling the complex interplay of causal pathways, that analysis found significant effects for only one of six selected proximal risk and protective factor mediators assessed at posttest (sixth grade). These earlier findings suggested the application of a more parsimonious approach that focused solely on mediation of intervention effects on young adult outcomes through substance initiation growth factors.
As part of a broad spectrum evaluation, three major kinds of problematic substance use were examined in the current study, namely, those related to alcohol, cigarettes, and illicit drugs. A fourth measure that was examined pertained to polysubstance use, an index combining use of the three types of substances. In addition, a measure of problematic health and social outcomes associated with alcohol use was examined. The primary analysis entailed an indirect effects model to predict problematic young adult substance use. As part of an additional set of analyses used to evaluate the practical significance of intervention effects, dichotomous caseness outcomes also were evaluated, as further described below. Consistent with the posited developmental model, it was hypothesized that intervention effects on problematic young adult substance use would occur primarily indirectly, via intervention effects on adolescent substance initiation. Earlier research reports that used these data sets have found only positive or null intervention effects on substance outcomes across multiple waves of data spanning from early to late adolescence, suggesting directional study hypotheses with one-tailed tests of significance. Nonetheless, exact t values are presented so that two-tailed results are transparent.