Intervention research in anorexia nervosa - a plea for single case experimental designs.

Anorexia nervosa (AN) is a severe eating disorder and among the mental disorders with the highest mortality rate. To date, not much is known about its development and maintenance, and treatment outcomes are improvable. At the same time, research on psychological interventions for AN is a complicated endeavor, often characterized by small sample sizes and methodological heterogeneity, which impedes the comparison and evaluation of treatment outcomes. In this paper, several population-related, therapist-related and methodological challenges that may be encountered during research on psychological interventions for AN are discussed. The use of single case experimental designs (SCEDs), which could account for several of these challenges, is suggested as a complementary approach to current methods of assessing treatment efficacy. The use of SCEDs could be beneficial to the field, by contributing to the knowledge about AN and to the development and evaluation of better treatments, which are sorely needed.