Acceptance and Commitment Therapy - Evidence

Evidence

ACT had, as of October 2006, been evaluated in about 30 controlled time series studies or randomized clinical trials for a variety of client problems. As of 2011 that number has about doubled and new controlled studies are now appearing very regularly. Overall, when compared to other treatments designed to be helpful, the effect size for ACT is a Cohen's d of around 0.6 which is considered a medium effect size. In some studies ACT has exceeded the performance of gold standard treatments, in others it has been equally effective, and in one or two studies with minor problems it has not done as well. As compared to treatments that are already known to be effective, the effect size so far is about .3, which is small. Across the whole empirical clinical psychology literature the average effect size for such comparisons approaches zero, however. All of these comparison and their effect sizes need to be viewed with caution, because many of the trials are unfunded and are based on a relatively small number of patients; and in some cases might be contaminated by the allegiance effect. A large and well done trial by a major CBT research team on mixed anxiety disorders that showed superiority of ACT to gold standard CBT on the primary outcome measure has recently appeared however and in that study allegiance effects should have worked in the opposite direction, suggesting that at least some of the effects in favor of ACT are replicable by teams that are skeptical of this approach

In recent years larger and better controlled trials have begun to appear and the number of areas to which it has been successfully applied is growing. ACT is considered an empirically validated treatment by the American Psychological Association, with the status of "Modest Research Support" in depression and "Strong Research Support" in chronic pain, with several others specific areas such as psychosis and work site stress currently under review. ACT is also listed as evidence-based by the Substance Abuse and Mental Health Services Administration of the United States federal government which has examined randomized trials for ACT in the areas of psychosis, work site stress, and obsessive compulsive disorder, including depression outcomes.

ACT is still relatively new in the development of its research base with the randomized trials beginning in earnest only after the 1999 publication of the original book on ACT. ACT has shown preliminary research evidence of effectiveness in randomized trials for a variety of problems including chronic pain, addictions, smoking cessation, depression, anxiety, psychosis, workplace stress, diabetes management, weight management, epilepsy control, self-harm, body dissatisfaction, eating disorders, burn out, and several other areas. ACT has more recently been applied to children, adolescents and trainees, with good results.

Mediational analyses have provided evidence for the possible causal role of key ACT processes, including acceptance, defusion, and values, in producing beneficial clinical outcomes. Correlational evidence has also found that absence of these processes predicts many forms of psychopathology. A recent meta-analysis showed that ACT processes, on average, account for 16–29% of the variance in psychopathology (general mental health, depression, anxiety) at baseline, depending on the measure, using correlational methods . A recent meta-analysis of 68 laboratory-based studies on ACT components has also provided support for the link between psychological flexibility concepts and specific components