In this study we are concerned about the first dimension—treatment efficacy. In order to evaluate the efficacy of interventions for reducing distress in parents of children with developmental disabilities, we focus on randomized or quasi-randomized trials. Levant [2005] asserted, ‘‘Randomized clinical trials and their logical equivalents are the standard for drawing causal inferences about the effects of interventions ...’’ (p. 8). In order to go beyond the claim that a treatment method is evidence-based, we also evaluate whether or not interventions can be considered to be well established, probably efficacious, or unproven. For a treatment to be considered ‘‘well established,’’ two or more studies must show that it is superior to medication, placebo, or an alternative treatment or that it is equivalent to an already established treatment, or nine single-subject case studies must be conducted to establish its equivalence or superiority .... For an intervention to be considered ‘‘probably efficacious,’’ two or more studies must show it to be superior to a wait-list control condition or one experiment must meet the criteria for a well-established treatment, or three single-case studies must be conducted [Hoagwood et al., 2001, p. 1179].