A Psychobehavioural Perspective on the Eating Disorders Self-starvation and physical activity The eating disorders as addiction Vulnerability Current Research Physical Activity and the Eating Disorders Approximately 80% of patients with AN, and 55% with BN, are hyperactive during their disorder (Davis et al., 1997). Competitive sport/assiduous exercise precedes dieting in > half of eating-disordered patients (Davis et al., 1994). The strongest predictor of a chronic outcome in AN is a compulsive drive to exercise at the termination of treatment ( Strober et al., 1997). Excessive exercisers display significantly greater psychopathology than non-exercising patients (Davis et al., 1998). Cultural Standard of Female Attractiveness Fashion industry Entertainment media Fitness and health promotion. Childrens toys. Activity-Induced Anorexia Wheel Rotations Body Weight Days Food restricted Access to a running wheel Days Body Weight Amount of Exercise Days Body Weight Human Starvation Study AN Patients Spontaneous Anorexia Self-starvation Hyperactivity Occasional bingeing Successful treatment with 5-HT drugs Mostly female The Eating Disorders as Addiction a.Increasingly compulsive nature of the behaviours b.Continuation of the behaviour in the face of adverse consequences to health. c.A strong craving to resume the behaviour after termination. d.High relapse after treatment. Age of symptom onset: 16 18 years Davis, Kennedy, Ralevski, & Dionne (1994) The role of physical activity in the development and maintenance of eating disorders. Psychological Medicine, 24, Anhedonia The diminished ability to experience pleasure or reward from conventional reinforcers. 1. Personality Trait Genetic predisposition Low dopamine [DA] availability in the mesolimbic common reward pathway of the brain. 2. State-induced Characteristic Neuroleptic drugs Chronic stimulation of mesolimbic DA Stress Drug Self-Administration Increased locomotion, in response to stress, reliably predicts the degree to which animals will self- administer psychomotor stimulant drugs (e.g. cocaine, alcohol, amphetamine). Vulnerability to Addiction To a dose of cocaine, low DA receptor density in the reward pathway was associated with the experience of pleasure (Volkow et al., 1999). Some anhedonics engage in compensatory behaviours that elevate mesolimbic DA (Carton et al., 1995). Predictions 1.AN patients would be more anhedonic than BN patients and normal controls. 2.Those who exercise excessively would be more anhedonic than non-exercisers. 3.Anhedonia would have both trait and state relevance to the eating disorders. Subjects Anorexia Nervosa Bulimia Nervosa NOS- history AN EE NE Analyses of Covariance (ANCOVA) Anhedonia = Group (AN vs BN) + Exercise Status (EX vs Non-Ex) + [Group x Exercise Status] + Depression. Physical Anhedonia Anorexia Nervosa vs Bulimia Nervosa Group x Exercise Status: F 1, 146 = 7.52, p = * Physical Anhedonia Anorexia Nervosa vs NOS Group x Exercise Status: F 1, 104 = 4.00, p = * Stimulate the -endorphin system which in turn activates the mesolimbic dopamine [DA] system. Arcuate Nucleus Of the Hypothalamus - EP Ventral Tegmental Area Nucleus Accumbens + DA - GABA GABA - DA Overeating Eating to Regulate Mood Variable BetaSE t p < (Constant) Anhedonia Neuroticism R 2 = 0.14 N = 200 undergraduate males and females Conclusions AN patients are more anhedonic than BN patients. Exercise may be a compensatory behaviour for anhedonia. For some, an enhanced ability to experience pleasure leads to overeating. Conclusions Severe dieting may induce a state of anhedonia. Low anhedonic traits may facilitate recovery. Exercise can compensate for, and contribute to, a state of anhedonia.