At present, the majority of studies investigating the effectiveness of early intervention programs are plagued with shortcomings in research design. Namely, most of these studies do not have control and comparison groups, do not use random assignment, have small sample sizes, and have high dropout rates (Finkelhor & Berliner, 1995; Gilliam & Zigler, 2000 Kaplan et al., 1999; MacMillian, 2000). Additionally, studies often use proxy variables such as placement status (e.g., whether the child is placed in the home, foster care, etc.) as an indicator of treatment effectiveness, instead of measuring objective child and parenting outcomes such as improved parenting behaviors and the child's social, cognitive, emotional, and behavioral functioning (see Clyman, Harden, & Little, 2002). Future program evaluations should strive to correct these limitations by using control groups and measuring more direct child outcomes.
Empirical efforts are also needed to examine which interventions are beneficial for specific populations (Fisher et al., 2005; Guralnick, 2005). In particular, specific maltreatment type, child age, presenting problems, and family characteristics are all potentially important conditions. In addition, identifying specific treatment components (active ingredients) responsible for producing desired effects will further advance our understanding of treatment outcomes. These streams of research not only will inform which treatments to pursue, replicate, and encourage but also will identify which treatments will benefit which group of maltreated children most. Information gathered concerning treatment components and subgroups of maltreated populations can lead to more efficient use of limited financial and human resources.
Nevertheless, the available research offers significant reason to believe that a variety of gains are achievable from well-conceptualized, well-delivered, and enduring interventions for maltreated children, particularly when these interventions are started as early as possible. It is impractical to think that participation of maltreated infants, toddlers, and preschoolers in an abbreviated early intervention program will prepare them for school and inoculate them from all problematic behavior. Rather, benefits are likely to emerge when children receive a large dose of high-quality, comprehensive, early intervention treatment that lasts throughout the elementary school years (Brooks-Gunn, 2003). Lasting gains that maltreated children younger than the age of 3 years may receive from early intervention are likely to be undermined if environmental circumstances remain inadequate. Therefore, issues related to poverty (e.g., lack of quality public education, lack of safe housing, unemployment, low wages, stress, dysfunctional coping) are all important components to consider when attempting to increase the likelihood of short-term and long-term early intervention success (Brooks-Gunn, Fuligni, & Berlin; 2003; Espinosa, 2002; McAlpine, Marshall, & Doran, 2001).