A Psychobehavioural Perspective on the Eating Disorders

1
A Psychobehavioural Perspectiveon the Eating
Disorders

• Self-starvation and physical activity
• The eating disorders as addiction
• Vulnerability
• Current Research

2
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 gt 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).

3
Cultural Standard of Female Attractiveness

• Fashion industry
• Entertainment media
• Fitness and health promotion.
• Childrens toys.

4
Activity-Induced Anorexia
Body Weight
Food restricted
Wheel Rotations
Days
Access to a running wheel
5
Human Starvation Study
AN Patients
Body Weight
Days
Amount of Exercise
Body Weight
Days
6
Spontaneous Anorexia

• Self-starvation
• Hyperactivity
• Occasional bingeing
• Successful treatment with 5-HT drugs
• Mostly female

7
The Eating Disorders as Addiction

• Increasingly compulsive nature of the behaviours

• Continuation of the behaviour in the face of
  adverse consequences to health.

• A strong craving to resume the behaviour after
  termination.

• High relapse after treatment.

8
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, 957-967
9
Anhedonia

• The diminished ability to experience pleasure or
  reward from conventional reinforcers.
• Personality Trait
• Genetic predisposition
• Low dopamine DA availability in the mesolimbic
  common reward pathway of the brain.
• State-induced Characteristic
• Neuroleptic drugs
• Chronic stimulation of mesolimbic DA
• Stress

10
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).
11
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).

12
Some anhedonics engage in compensatory behaviours
that elevate mesolimbic DA (Carton et al., 1995).
13
Predictions

• AN patients would be more anhedonic than BN
  patients and normal controls.
• Those who exercise excessively would be more
  anhedonic than non-exercisers.
• Anhedonia would have both trait and state
  relevance to the eating disorders.

14
Subjects
EE
NE
15
Analyses of Covariance(ANCOVA)
Anhedonia Group (AN vs BN) Exercise Status
(EX vs Non-Ex) Group x Exercise Status
Depression.
16
Physical AnhedoniaAnorexia Nervosa vs Bulimia
Nervosa

Group x Exercise Status F1, 146 7.52, p
0.0069
17
Physical AnhedoniaAnorexia Nervosa vs NOS

Group x Exercise Status F1, 104 4.00, p
0.0482
18
Stimulate the ?-endorphin system which in turn
activates the mesolimbic dopamine DA system.
19
Arcuate Nucleus Of the Hypothalamus
?-EP
- GABA GABA - DA
DA
Ventral Tegmental Area
Nucleus Accumbens
20
Eating to Regulate Mood
Overeating
N 200 undergraduate males and females
R2 0.14
21
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.

22
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.