PSYCHOLOGY 8: Eating Disorders (AN, BN, BED)

Advanced Psychology ESL – Clinical Features, Neurobiology & Treatment Mechanisms

1. Introduction

Eating disorders involve disturbances in:

  • eating behaviour

  • body image

  • weight regulation

  • emotional and cognitive processes

They have the highest mortality rate of any psychiatric condition and require coordinated medical and psychological care.

The main DSM-5 eating disorders include:

  • Anorexia Nervosa (AN)

  • Bulimia Nervosa (BN)

  • Binge Eating Disorder (BED)

Scientific Expansion: Why Eating Disorders Are Lethal

Medical risks include:

  • cardiac arrest (electrolyte imbalance → arrhythmia)

  • organ failure (from starvation)

  • increased suicide risk (especially in AN and BN)

Neurobiologically, starvation alters:

  • serotonin and dopamine

  • decision-making

  • hunger/satiety signalling

  • reward circuitry

This creates a self-reinforcing loop where the disorder becomes harder to treat the longer it persists.

2. Anorexia Nervosa (AN)

A serious disorder characterised by:

  • persistent restriction of energy intake

  • significantly low body weight

  • intense fear of gaining weight

  • distorted body image

Core features

  • inability to maintain minimally healthy weight

  • fear of weight gain

  • distorted self-perception

  • preoccupation with calories, exercise, rituals

  • perfectionism, rigidity

  • severe medical complications

DSM-5 subtypes:

  • Restricting type

  • Binge–purge type

Etiology

  • genetic vulnerability

  • perfectionism, high harm avoidance

  • altered serotonin signalling

  • trauma or chronic stress

  • cultural pressure

  • overactivation of self-control circuits

Medical risks

  • bradycardia

  • arrhythmias

  • electrolyte imbalance

  • osteoporosis

  • hypothermia

  • cognitive impairment

  • organ failure

AN is life-threatening and requires medical monitoring.

Treatment

  • nutritional rehabilitation

  • family-based therapy (FBT)

  • CBT-E

  • DBT for emotional regulation

  • medical stabilisation

  • restructuring distorted beliefs

Scientific Expansion: Neurobiology of AN

Brain circuits involved:

  • Cognitive control network (PFC) → overactive

  • Reward system (dopamine) → reduced response to food

  • Insula dysfunction → impaired interoceptive awareness (hunger signals)

  • Serotonin imbalance → anxiety, rigidity

Starvation worsens:

  • obsessionality

  • rigidity

  • anxiety

This makes the disorder self-perpetuating.

3. Bulimia Nervosa (BN)

BN involves cycles of binge eating followed by compensatory behaviours.

Core features

  • binge episodes (loss of control + large food volume)

  • compensatory behaviours (purging, fasting, exercise)

  • overvaluation of weight/shape

  • guilt and secrecy

  • usually normal or overweight

Etiology

  • emotional dysregulation

  • bingeing as escape from negative emotion

  • perfectionism

  • impulsivity

  • serotonin/dopamine dysregulation

  • history of restriction

Medical complications

  • electrolyte imbalance

  • dehydration

  • acid erosion of teeth

  • GI injury

  • cardiac complications

  • swollen salivary glands

Treatment

  • CBT-E (first-line)

  • DBT

  • SSRIs (fluoxetine at higher doses)

  • nutritional stabilisation

BN responds well to early intervention.

Scientific Expansion: Neurobiology of BN

  • Dopamine hypersensitivity → strong reward “surge” during bingeing

  • Serotonin deficiency → impulsivity + poor satiety signals

  • Hunger–fullness signalling disrupted (hypothalamus pathway)

  • Stress-response dysregulation → bingeing used as emotional numbing

BN = emotion-driven impulsive behaviour + reward dysregulation.

4. Binge Eating Disorder (BED)

BED involves recurrent binge episodes without compensatory behaviours.

Core features

  • loss of control when eating

  • rapid eating

  • eating until uncomfortably full

  • eating when not hungry

  • eating alone due to embarrassment

  • guilt and distress

Weight is not diagnostic (can be normal, overweight, or obese).

Etiology

  • dopamine reward dysfunction

  • emotional eating linked to trauma or stress

  • impulsivity

  • bingeing as coping

  • chronic dieting patterns

Treatment

  • CBT-E

  • DBT

  • mindfulness/intuitive eating

  • SSRIs or lisdexamfetamine (in some countries)

  • behavioural weight management if appropriate

BED often responds well to psychological intervention.

Scientific Expansion: Neurobiology of BED

  • Overactive reward pathways → strong dopamine response to food

  • Underactive inhibitory control networks → difficulty stopping eating

  • Stress-related cravings → comfort eating to regulate emotions

BED combines reward seeking, emotional regulation problems, and habit loops.

5. Transdiagnostic Features of Eating Disorders

Shared elements across AN, BN, BED include:

  • overvaluation of weight/shape

  • cognitive distortions

  • emotional dysregulation

  • diet–binge cycle

  • interoceptive deficits

  • low self-esteem, self-criticism

Scientific Expansion: The Diet–Binge Cycle Explained

Restrictive dieting causes:

  1. physiological deprivation → hunger hormones ↑

  2. psychological deprivation → cravings ↑

  3. loss of control → binge

  4. guilt + shame → renewed restriction

This is the engine that powers BN and BED.

6. Biological Mechanisms

Genetic factors

Strong heritability, especially in AN and BED.

Dopamine reward dysfunction

  • AN: reduced reward from eating

  • BN/BED: exaggerated reward → bingeing

Serotonin imbalance

Involved in mood, impulse control, satiety.

Brain circuitry differences

  • AN: overactive PFC (excessive self-control)

  • BN/BED: impaired inhibition + strong food cue sensitivity

Starvation effects

Starvation worsens anxiety, rigidity, and obsessionality in AN.

7. Treatment Approaches Across Eating Disorders

CBT-E

Most evidence-based transdiagnostic treatment.

Family-Based Treatment (FBT)

Highly effective for adolescents with AN.

DBT

Helpful for bingeing, purging, and emotional dysregulation.

Nutritional rehabilitation

Essential for restoring brain function.

Medical monitoring

Vital due to cardiovascular/metabolic risks.

Medication

  • SSRIs → BN and BED

  • Lisdexamfetamine → BED

  • Limited medication benefit → AN

Best outcomes = multidisciplinary team.

Scientific Expansion: How Treatments Work

CBT-E

  • modifies unhelpful beliefs

  • normalises eating patterns

  • interrupts diet–binge cycle

FBT

  • empowers family to re-feed

  • reduces avoidance and fear

  • restores weight → restores brain function

DBT

  • builds distress tolerance

  • reduces impulsive binge/purge behaviour

Nutrition rehabilitation

  • improves cognition, mood

  • reverses starvation effects

  • restores hormone balance

8. Key Academic Vocabulary

  • binge eating

  • compensatory behaviours

  • restriction

  • purging

  • body image distortion

  • interoceptive awareness

  • malnutrition effects

  • cognitive rigidity

  • perfectionism

  • CBT-E

  • starvation syndrome

  • emotional regulation

9. Discussion Questions

  • What distinguishes AN from BN?

  • Why does dieting often trigger binge eating?

  • How do perfectionism and rigidity contribute to AN?

  • Why can BN occur in individuals with normal weight?

  • How does CBT-E address core beliefs in eating disorders?

  • What role does emotional regulation play in BED?

  • Why is medical monitoring essential in AN?

10. Case Studies & Clinical Reasoning

Case Study 1: Anorexia Nervosa

A 17-year-old girl has lost 15 kg in six months. She denies being underweight and fears “getting fat.” She exercises secretly at night and eats only 300–500 calories/day. Heart rate is 42 bpm.

Questions

  1. Which DSM-5 criteria for AN does she meet?

  2. What medical risks require urgent monitoring?

  3. Why is FBT recommended in adolescence?

  4. How is her body image distortion maintained by starvation?

Case Study 2: Bulimia Nervosa

A 24-year-old woman binge eats large amounts of food at night and induces vomiting to “undo it.” She has normal weight, swollen cheeks, and dental erosion.

Questions

  1. What core symptoms indicate BN over AN?

  2. How does restriction contribute to her binge–purge cycle?

  3. Why is high-dose fluoxetine effective?

  4. What cognitive distortions might she show?

Case Study 3: Binge Eating Disorder

A 28-year-old man eats rapidly until uncomfortably full several times per week. He does not purge but feels shame and avoids eating with others. His binges occur when stressed.

Questions

  1. Why is this BED and not BN?

  2. Which emotional regulation problems are present?

  3. Which treatment approaches would best help him?