3.8 Feeding/Eating, Sleep-Wake, and Somatic Symptom Disorders

Feeding and Eating Disorders

Feeding and eating disorders are characterized by a persistent disturbance of eating or eating-related behavior that results in the altered consumption or absorption of food and significantly impairs physical health or psychosocial functioning.

1. Anorexia Nervosa (AN)

• DSM-5-TR Diagnostic Criteria:
  1. Restriction of energy intake relative to requirements, leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health (defined as a BMI < 18.5 kg/m² in adults or BMI-for-age percentile < 5th percentile in children/adolescents).
  2. Intense fear of gaining weight or of becoming fat, or persistent behavior that interferes with weight gain, even though at a significantly low weight.
  3. Disturbance in the way in which one's body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight.
• Subtypes:
  • Restricting Type: During the last 3 months, weight loss is accomplished primarily through dieting, fasting, and/or excessive exercise. No recurrent binge eating or purging.
  • Binge-Eating/Purging Type: During the last 3 months, the individual has engaged in recurrent episodes of binge eating or purging behavior (self-induced vomiting, misuse of laxatives, diuretics, or enemas).
• BMI Severity Index (Adults): Mild (BMI ≥ 17 kg/m²), Moderate (BMI 16–16.99 kg/m²), Severe (BMI 15–15.99 kg/m²), Extreme (BMI < 15 kg/m²).
• Physical Exam Findings: Hypothermia (< 36°C / 96.8°F), sinus bradycardia (< 50 bpm), hypotension (< 90/60 mmHg), orthostatic BP drops, lanugo (fine, soft neonatal-type hair on trunk/extremities), dry skin, peripheral edema, salivary gland hypertrophy (parotid enlargement), amenorrhea (no longer a mandatory DSM-5-TR criterion, but common).
• Laboratory & Electrocardiogram (ECG) Abnormalities: Leukopenia, anemia, thrombocytopenia, elevated BUN (dehydration), hypokalemia, hypomagnesemia, hyponatremia, hypoglycemia, elevated LFTs, decreased T3 (euthyroid sick syndrome), prolonged QTc interval, ST-segment depression, T-wave inversion, and U waves on ECG.
• Indications for Immediate Medical Hospitalization:
  • Heart rate < 40 beats per minute
  • Blood pressure < 90/60 mmHg or severe orthostatic changes (HR increase > 20 bpm, BP drop > 10 mmHg)
  • Cardiac arrhythmias or prolonged QTc
  • Body temperature < 36°C (96.8°F)
  • Body weight < 75% of ideal body weight (BMI < 15 kg/m²)
  • Hypokalemia (< 3.0 mEq/L), hypophosphatemia, or severe electrolyte derangement
  • Intractable purging or refusal to eat

The Refeeding Syndrome Emergency

Refeeding Syndrome is a critical, life-threatening metabolic complication occurring when nutrition (oral, enteral, or parenteral) is reintroduced to a severely malnourished patient.

• Pathophysiology: Malnourishment induces a catabolic state with depleted intracellular stores of phosphate, potassium, and magnesium. Reintroducing carbohydrates stimulates a rapid insulin surge. Insulin shifts glucose, phosphate, potassium, and magnesium from extracellular space into the cells to support glycolysis and protein synthesis.

• Hallmark Laboratory Finding: Severe, precipitous HYPOPHOSPHATEMIA (along with hypokalemia and hypomagnesemia).

• Clinical Manifestations: Cardiac dysrhythmias, acute heart failure, pulmonary edema, seizures, delirium, rhabdomyolysis, neuromuscular paralysis, and sudden cardiac death.

• Prevention & PMHNP Management: Reintroduce calories slowly (10–15 kcal/kg/day), monitor serum electrolytes (phosphate, potassium, magnesium) daily, supplement electrolytes prior to and during refeeding, and restrict sodium and fluid intake initially.

• Treatment Protocols for AN:

  • Psychotherapy: Family-Based Treatment (FBT / Maudsley Approach) is the gold-standard first-line treatment for adolescents, empowering parents to manage weight restoration. Enhanced Cognitive Behavioral Therapy (CBT-E) for adults.
  • Pharmacotherapy: No FDA-approved medications exist for AN core symptoms. Olanzapine (Zyprexa) (2.5–10 mg daily) is used off-label to promote weight gain, attenuate obsessive food-related anxiety, and reduce agitation.
  • CONTRAINDICATION WARNING: Bupropion (Wellbutrin) is strictly CONTRAINDICATED in Anorexia Nervosa and Bulimia Nervosa due to a high risk of drug-induced grand mal seizures.

2. Bulimia Nervosa (BN)

• DSM-5-TR Diagnostic Criteria:
  1. Recurrent episodes of binge eating (eating in a discrete period an amount of food definitely larger than most people would eat, with a sense of lack of control).
  2. Recurrent inappropriate compensatory behaviors to prevent weight gain (self-induced vomiting, laxative, diuretic, or other medication misuse, fasting, or excessive exercise).
  3. Both occur, on average, at least once a week for 3 months.
  4. Self-evaluation is unduly influenced by body shape and weight.
  5. Does not occur exclusively during episodes of Anorexia Nervosa (patients are typically at normal weight or overweight, BMI ≥ 18.5 kg/m²).
• Physical Exam Signs:
  • Russell's Sign: Calluses or abrasions on the dorsal surface of the hand/knuckles from repeated contact with incisor teeth during self-induced vomiting.
  • Sialadenosis: Bilateral painless hypertrophy of the parotid salivary glands.
  • Dental Enamel Erosion: Loss of dental enamel on the lingual surfaces of anterior teeth from exposure to gastric acid.
• Laboratory Profile: Hypokalemic, hypochloremic metabolic alkalosis (from loss of gastric HCl via vomiting). Note: Excessive laxative abuse leads to hypokalemic metabolic acidosis (loss of bicarbonate via stool).
• Pharmacotherapy: Fluoxetine (Prozac) 60 mg daily is the ONLY FDA-approved medication for Bulimia Nervosa. Higher doses (60 mg) are required compared to depression dosing. Reduces bingeing and purging frequency.

3. Binge-Eating Disorder (BED)

• Diagnostic Criteria: Recurrent episodes of binge eating occurring at least once a week for 3 months, associated with ≥3: eating much more rapidly than normal, eating until uncomfortably full, eating large amounts when not hungry, eating alone due to embarrassment, feeling disgusted/depressed/guilty afterward. NO regular use of inappropriate compensatory behaviors.
• Treatment: CBT-E, Interpersonal Psychotherapy (IPT).
• FDA-Approved Pharmacotherapy: Lisdexamfetamine (Vyvanse) (30–70 mg daily) is the only FDA-approved medication for moderate-to-severe BED. Off-label options: Topiramate, SSRIs.

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Sleep-Wake Disorders

1. Insomnia Disorder

• DSM-5-TR Diagnostic Criteria: Predominant complaint of dissatisfaction with sleep quantity or quality, associated with difficulty initiating sleep, difficulty maintaining sleep, or early-morning awakening with inability to return to sleep. Causes clinically significant distress or impairment. Occurs at least 3 nights per week for at least 3 months, despite adequate opportunity for sleep.
• Sleep Architecture: NREM Sleep (Stage N1 [light], Stage N2 [sleep spindles/K-complexes], Stage N3 [Slow-Wave/Delta sleep—restorative]), and REM Sleep (dreaming, muscle atonia). Aging reduces Stage N3 slow-wave sleep.
• First-Line Treatment: Cognitive Behavioral Therapy for Insomnia (CBT-I) is the gold-standard first-line treatment, superior to medications long-term. Components include:
  • Stimulus Control: Bed is strictly for sleep and sex. If unable to sleep after 20 minutes, get out of bed and perform a quiet activity in dim light until sleepy.
  • Sleep Restriction Therapy: Limiting time in bed to actual sleep duration to increase sleep efficiency.
  • Sleep Hygiene: Avoiding caffeine/alcohol near bedtime, maintaining consistent wake times, eliminating screens/blue light.
• Pharmacotherapy Guidelines:
  • Non-Benzodiazepine Hypnotics (Z-drugs): Zolpidem (Ambien), Eszopiclone (Lunesta), Zaleplon (Sonata). Act selectively on GABA-A alpha-1 subunit. Risk of complex sleep behaviors (sleep-walking, sleep-driving).
  • Dual Orexin Receptor Antagonists (DORAs): Suvorexant (Belsomra), Lemborexant (Dayvigo). Block wake-promoting orexin signaling.
  • Melatonin Receptor Agonists: Ramelteon (Rozerem) (MT1/MT2 agonist; no abuse potential).
  • Sedating Antidepressants: Doxepin low-dose (3–6 mg), Trazodone (25–100 mg), Mirtazapine (7.5–15 mg).

2. Obstructive Sleep Apnea (OSA) vs. Narcolepsy

• OSA: Repetitive upper airway collapse during sleep. Diagnosed via Polysomnography showing Apnea-Hypopnea Index (AHI) ≥ 5 with daytime sleepiness. Treatment: Continuous Positive Airway Pressure (CPAP). Avoid CNS depressants and sedating medications.
• Narcolepsy: Primary central sleepiness disorder caused by loss of hypothalamic hypocretin (orexin)-producing neurons.
  • Classic Tetrad: 1. Excessive Daytime Sleepiness (EDS); 2. Cataplexy (sudden loss of muscle tone triggered by strong emotions like laughter); 3. Sleep Paralysis; 4. Hypnagogic (falling asleep) or Hypnopompic (waking up) Hallucinations.
  • Treatment: Modafinil (Provigil) or Armodafinil (Nuvigil) for daytime sleepiness; Pitolisant (H3 antagonist) or Sodium Oxybate (Xyrem) (GABA-B agonist) for cataplexy.

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Somatic Symptom and Related Disorders: Differential Matrix

Clinical Management Principles for Somatic Disorders

1. Establish a Single Point of Care: Schedule regular, brief, structured appointments with one primary PMHNP/PCP (e.g., every 4–6 weeks) regardless of symptom severity.
2. Validate Distress Without Reinforcing Sickness: Acknowledge that the patient's physical pain/distress is real ("I can see how much pain this causes you") while avoiding unnecessary diagnostic workups, invasive procedures, or specialist referrals.
3. Psychotherapy: Cognitive Behavioral Therapy (CBT) focused on shifting focus from symptoms to coping mechanisms and stress reduction.