Counselling Psychology Quarterly Vol. 24, No. 1, March 2011, 71–82 The mediating and moderating effects of differentiation of self on body mass index and depressive symptomatology among an American college sample Lisa M. Hooper a * and Kirsten Doehler b a Department of Educational Studies in Psychology, Research Methodology, and Counseling, The University of Alabama, Box 870231, 315 B Graves Hall, Tuscaloosa, AL 35487-0231, USA; b Department of Mathematics and Statistics, Elon University, 2320 Campus Box, Elon, NC 27244, USA (Received 16 May 2010; final version received 17 November 2010) Differentiation of self – a core construct of Bowen’s (Bowen, M. (1978). Family therapy in clinical practice. New York: Jason Aronson) family systems theory – was examined as a possible predictor of psychological health and physical health and as a mediator and moderator of the relation between overall functioning and psychological health and physical health. A total of 818 American college students participated (mean age ¼ 23.72, SD ¼ 4.79) in this study. Differentiation of self was correlated and was predictive of psychological health, as measured by the Beck depression inventory, and physical health, as measured by body mass index (BMI). A multivariate multiple regression model revealed that differentiation of self partially mediated the effects of overall functioning on depressive symptomatology and on BMI. Results from a hierarchical regression model showed that differentiation of self moderated the relation between overall functioning and depressive symptomatology but did not moderate the relation between overall functioning and BMI. Taken together, these preliminary findings provide initial evidence of the importance of the associations between family systemic factors (differentiation of self) and psychological and physical health factors among American college populations. Keywords: Bowenian theory; differentiation of self; college health; psycho- logical health; physical health Introduction Bowen’s family systems theory (Bowen, 1978) is based on the premises that the individual’s primary purpose is to differentiate him or herself from the family of origin and that previous generations’ behavior and level of functioning are associated with this process in the current and future generations. Theoretically, differentiation of self pertains to the ability to maintain emotional objectivity during high levels of anxiety in a system while concurrently relating to key people in the system (family members, peers, coaches, professors, etc.; Bowen, 1978; Kerr & Bowen, 1988). According to Bohlander (1995) and Skowron and Friedlander (1998), four concepts *Corresponding author. Email: lhooper@bamaed.ua.edu ISSN 0951–5070 print/ISSN 1469–3674 online ß 2011 Taylor & Francis DOI: 10.1080/09515070.2011.559957 http://www.informaworld.com