Efficacy of Preventive Interventions for the Prevention of Substance Use
In terms of intervention efficacy, family based interventions, both alone and combined with child-centered interventions (family-based + child-centered interventions), generally have been found to be efficacious in preventing substance use in adolescents (e.g., Loveland-Cherry et al. 1999; Spoth et al. 1999a, b, 2002, 2004, 2005, 2006). However, findings concerning the efficacy of child-centered have been inconsistent. While three of the four family-based and two of three family-based + child-centered interventions and four of six multicomponent interventions that we reviewed reported significant intervention effects on substance use initiation, only 15 of 23 child-centered reviewed reported significant intervention effects on substance use initiation. In addition, 5 of the 15 efficacious child-centered interventions and one of four efficacious multicomponent interventions reported that the efficacy of the intervention was limited to a subgroup of participants (e.g., Hispanics boys: Unger et al. 2004; boys: Brown et al. 2002; girls: Lillehoj et al. 2004; Palinkas 1996) or locations (e.g., Portugal: De Vries et al. 2006; inner city magnet school: Werch et al. 2000). In summary, the findings concerning the efficacy of child-centered, family-based, and multicomponent preventive interventions for substance use initiation are mixed.
In contrast, findings concerning the efficacy of family based + child-centered interventions hold promise. Recent trials comparing a family based + child-centered intervention to an inert control condition (Spoth et al. 2002, 2004, 2005, 2006) and to child-centered only intervention (i.e., LST only: Spoth et al. 2002, 2005) suggest that the combined family based + child-centered intervention (i.e., SFP and LST + SFP) was more efficacious in preventing adolescent substance use initiation than control and the child-centered only intervention (Spoth et al. 2002, 2004, 2005, 2006). Spoth et al. (2002) compared LST only and LST + SFP to an inert control condition and found that, although both LST alone and LST + SFP were efficacious in preventing marijuana initiation compared to an inert control, youth who had received LST + SFP had the lowest rate of alcohol initiation, compared to youth in the LST alone and control conditions, at post intervention. In addition, 1-year later (9th grade), youth in the LST + SFP group had a slower rate of increase of substance use initiation than youth in either the LST alone or control groups (Spoth et al. 2005). These results suggest that the combined child-centered and family based intervention may be more efficacious than child-centered alone for preventing adolescent substance use initiation.
In another study conducted by Spoth et al. (2004, 2006), SFP was compared to Preparing for the Drug Free Years (Catalano et al. 1999), a family-based intervention, and an inert control. No significant intervention effects were found between PDFY and the inert control while SFP was found to significantly decrease initiation of alcohol use, smoking, and drug use into the last year of high school (Spoth et al. 2004, 2006). Results from this study are promising in that they suggest that the effects of SFP may extend into 12th grade.
While Spoth and colleagues have extended the evaluation intervention efficacy into late adolescence, there is a paucity of research regarding long-term follow-up for preventive interventions. This is problematic because substance use initiation continues through the high school years (Johnston et al. 2006a). It would seem that studies that continue to assess substance use initiation in the last years of high school and into emerging adulthood would be most likely to capture more of the youth who are likely to initiate and would be the best indicator of intervention efficacy. Indeed, some intervention studies that have assessed adolescents through their senior year of high school have found decreases in intervention gains between the end of the intervention and participants' senior year in high school (e.g., Perry et al. 2002; Shope et al. 1998). We now turn to findings from studies examining preventive intervention effects at long-term follow-up.
We found only eight studies that examined intervention efficacy at 11th grade or later (Aveyard et al. 2001; Lynam et al. 1999; Palinkas 1996; Peleg et al. 2001; Peterson et al. 2000; Spoth et al. 2004, 2006; Zavela et al. 2004). Details on these studies are presented below by intervention type.
Of the 23 child-centered interventions reviewed, only four were found that examined the effects of the preventive intervention into late adolescence (Aveyard et al. 2001; Lynam et al. 1999; Palinkas 1996; Peleg et al. 2001; Peterson et al. 2000) and only one study reported significant intervention effects (Positive Adolescent Life Skills + Facts of Life; Palinkas 1996). However, results concerning the efficacy of Positive Adolescent Life Skills (PALS) + Facts of Life (Palinkas 1996), a child-centered school-based intervention delivered to girls, compared to Facts of Life alone were mixed. PALS + Facts of Life combined two interventions (i.e., PALS and Facts of Life) during a 16-week period. PALS used cognitive and behavioral techniques to improve social skills and to restructure social networks with the aim of preventing drug use in girls who were pregnant or were teen parents. Facts of Life was a 16-week normative education intervention. PALS + Facts of Life was found to be more efficacious in preventing cigarette and other drug initiation (e.g., cocaine, LSD, and amphetamines) at 3-month follow-up (14-19 years old) than Facts of Life alone. However, girls who had received the PALS + Facts of Life intervention were more likely have initiated alcohol and marijuana, at 3-month follow-up, than girls who receive Facts of Life alone.
Preparing for the Drug Free Years (PDFY; Catalano et al. 1999) is a family based intervention based on the social development model and was the only family-based intervention found that examined intervention efficacy into the 11th grade or beyond. This intervention focused on enhancing parent-child protective interactions through the use of four parent sessions. In addition, one parent-child session focused on peer resistance skills. Although PDFY was found to be efficacious in preventing substance use initiation at 2 years post intervention (8 grade), these effects were not maintained at the 4-year follow up (12th grade) (Spoth et al. 1999a, 2004).
Family-based + Child-centered Interventions
The Iowa Strengthening Families Program (ISFP; Molgaard and Spoth 2001) is primarily a family-based intervention. However, it does include a child-centered component. ISFP is based on the biopsychosocial model and on other empirically supported risk and protective factors models, and it is administered to parents and children concurrently. The aim of the intervention is to increase youth resistance skills, improve parenting practices, and strengthen families (e.g., parent/child communication, parenting, and parental monitoring of peer activities). The parent and child attend separate but concurrent six-session groups. The content of child sessions mirrors the content of most of the parent sessions (e.g., effective communication) and also includes child-centered sessions regarding peer relationship and resistance skills. In this respect, the ISFP includes some aspects of a child-centered intervention. After each separate child and parent session, a joint parent-child session is conducted where the parent and child practice the skills learned in their individual groups. The seventh and last session is a joint parent-child session. As mentioned earlier, ISFP has been found to significantly decrease initiation of alcohol use, smoking, and drug use into the last year of high school (Spoth et al. 2004, 2006).
Only five interventions were found that included several components, and only one of these interventions examined the efficacy of the intervention at 11th grade or beyond (Zavela et al. 2004). Say Yes First is a school based school based multi-component preventive intervention administered to youth during 4th through 8th grades (Zavela et al. 2004). The intervention included several components in addition to the child centered health education curriculum, including leadership training, case management, parent education, family and school activities, and academic tutoring (see Zavela et al. 1997, for a full description of the intervention). Zavela et al. (2004) found that lifetime prevalence of marijuana use in 11th grade was significantly lower for the Say Yes First intervention compared to the no-intervention control. No significant differences were found between Say Yes First and the no intervention control for the lifetime prevalence of alcohol. Smoking outcomes were not examined in this study. Given the paucity of research concerning the long term efficacy of child centered prevention programs, and given the relative lack of efficacy in those studies that have been conducted, it might be stated that the efficacy of child-centered programs, particularly in the long term, is tenuous at best. More research is clearly needed in this area.
In summary, results from the limited number of child-centered and family-based studies that followed youth into late adolescence or emerging adulthood did not support the long-term efficacy of these interventions. However, it also seems that the efficacy of child-centered and family-based interventions may be improved with the addition of other components (i.e., Zavela et al. 2004) or by combining both types of interventions (i.e., Spoth et al. 2004, 2006). It is worth noting that family-based + child-centered interventions that include decision-making in the context of peer resistance skills and are administered to parents and youth offer the most promising long-term results as evidenced by the wide-ranging effects (i.e., initiation of alcohol use, smoking, and drug use). Given the wide-ranging results observed with family-based + child-centered interventions, the lack of consistent long-term support for either child-centered or family-based only interventions raise several questions. Researchers have begun to question why widely used, and in many cases empirically supported, interventions are not more efficacious in preventing or reducing adolescent substance use in the long term (Gorman 2002). One potential explanation for the lack of long-term efficacy of child-centered interventions, in particular, involves the possibility that these interventions are not developmentally appropriate for adolescents because, although they seem to be efficacious in preventing substance use initiation in the short-term, these gains are not maintained into late adolescence and early adulthood.
This assumption of developmental inappropriateness is grounded in adolescents' emerging but still incomplete cognitive and neurological development that may not support the consistent employment of the decision-making skills promoted in child-centered interventions. Recent advances in the study of neuroscience, particularly studies using functional MRI to examine neurological structures, have allowed scientists to examine neurological development throughout adolescence. Findings from research in this area support the notion that, throughout adolescence, youth are still developing their ability to reason, make decisions, and process emotional information (Casey et al. 2002; Durston et al. 2006; Luna and Sweeney 2004). The prefrontal cortex, which is primarily responsible for many of these functions, does not fully mature until the mid-twenties (e.g., Casey et al. 2000; Luna and Sweeney 2004; Thompson et al. 2000).
Adding to the difficulties in decision-making associated with immature neurological development is the increasingly central role of peers in adolescence. Because adolescent substance use tends to take place in the presence of peers, and because peers are central in adolescents' decisions about whether to engage in substance use, decisions about whether to use substances likely take place in an emotionally charged or pressured environment. A result of immature neurological development and impaired decision making abilities may be an overestimation of the extent to which one's peers use substances and participate in other risky behaviors (Prinstein and Wang 2005). Immature neurological development and impaired decision making may also lead adolescents to underestimate the consequences associated with substance use, which has been reported in previous studies as an adolescent's sense of invulnerability to negative outcomes (Steinberg 2004). In turn, overestimating peer problem behavior and underestimating consequences of drug use have both been linked to initiation of substance use (D'Amico and McCarthy 2006).
Additionally, studies examining age-related changes in executive functioning have shown that, compared to adults, adolescents are not able to employ decision-making strategies on a consistent basis (reflected by more diffuse neurological activation in youth in comparison to adults), and they make more mistakes on cognitive tasks (Casey et al. 2000; Durston et al. 2006). As a consequence of the increased role of peers and of adolescents' immature cognitive development, adolescent reasoning, decision making, and emotion regulation may be particularly likely to break down when making decisions about whether to engage in substance use (Keating 1990; Reyna and Farley 2006). As a result, the efficacy of programs that encourage adolescents to make careful decisions based on critical thinking and problem solving skills, or based on changed attitudes and beliefs about substance use, without marshaling support from the social environment (e.g., parents, peers, society), may be undermined when adolescents find themselves in emotionally charged or peer-pressured situations (Steinberg 2007). The developmental status of the adolescent brain may contraindicate the use of child-centered programs that are not accompanied by a social-ecological component (Steinberg 2007).
In contrast, family-based interventions focus on family processes that serve a protective role for adolescent substance use by preventing exposure to high-risk situations and providing a support network through improved communication and parental involvement. However, findings from long-term evaluations suggest that family-based interventions alone may also not be sufficient (Spoth et al. 2004, 2006). Recent advances in adolescent neurological development may therefore have the potential to inform the development and refinement of substance use preventive interventions for adolescents by suggesting which modalities may and may not be appropriate for use with adolescents. In the remainder of this article, we discuss (a) relevant findings from research in adolescent neurological development and (b) implications of these findings for the development and refinement of interventions for preventing adolescent substance use.
J Prim Prev. 2008;29(1):5-35. © 2008 Springer
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Cite this: Adolescent Neurological Development and its Implications for Adolescent Substance Use Prevention - Medscape - Jan 01, 2008.