PSYCHOLOGICAL OR BEHAVIOURAL FACTORS AFFECTING DISORDERS OR DISEASES CLASSIFIED ELSEWHERE

1. Definition and nosology

ICD-11: 6E40 Psychological or behavioural factors affecting disorders or diseases classified elsewhere; DSM-5-TR: F54 Psychological Factors Affecting Other Medical Conditions — psychological factors interfering with somatic disease course (depression, anxiety, medication adherence, stress, beliefs about illness).

Distinct from factitious disorder (6D50) and somatic symptom disorder (6C20) — here there is a confirmed medical illness, but psychological factors influence the course.

2. History

• Alexander F. (1950) — conceptualization of ‘psychosomatic medicine’.
• Engel G.L. (1977) — ‘biopsychosocial model’.
• Levenson J.L. (2018) — APA Textbook of Psychosomatic Medicine.

3. Epidemiology

• Universal — psychological factors influence all chronic somatic diseases.
• Depression in cardiovascular disease — 20–40%; diabetes — 25%; cancer — 15–25%.
• Wide use of consultation-liaison psychiatry service.

4. Aetiology and pathogenesis

Biopsychosocial interaction — biological predisposition + psychological factors + social context.

5. Clinical features

• Comorbid depression/anxiety affects illness (e.g., increased mortality after myocardial infarction).
• Medication non-adherence (compliance/adherence).
• False beliefs about illness.
• Stress worsens illness course.
• Behavioral factors (smoking, alcohol, diet, physical inactivity).

6. Diagnosis

6.1 Unified diagnostic criteria

A. Confirmed medical illness present.

B. Psychological or behavioral factors interfere with illness course:

1. Reduces treatment response;
2. Increases health risk;
3. The pathophysiology is worsened;
4. Medical intervention alters the necessity.

C. Factitious, somatic symptom, not better explained by another mental disorder.

6.2 Source-specific clarifications

• DSM-5-TR / ICD-11 — same.
• Consultation-liaison psychiatry model.

6.3 Diagnostic algorithm

1. Evaluation of medical illness.
2. Identification of psychological factors — depression (PHQ-9), anxiety (GAD-7), medication adherence (Morisky).
3. Behavioral factors — smoking, alcohol, diet, physical activity.
4. Screening for comorbid psychiatric disorder.

6.4 Differential diagnosis

7. Examination and assessment

• PHQ-9, GAD-7, Morisky.
• Illness-specific scales (DDS — Diabetes Distress Scale, Beck-cardiac).

8. Treatment

1. An integrated multidisciplinary approach — somatic specialist + psychiatrist + psychologist.
2. Illness-specific psychosocial intervention:
   • Cardiac CBT (post-MI depression);
   • Diabetes self-management education (DSME);
   • Oncology distress monitoring;
   • Chronic pain CBT and ACT.
3. Antidepressant — disease-specific side effect profile:
   • Cardiac — sertraline, escitalopram;
   • Oncology — mirtazapine (sleep, appetite benefit);
   • Chronic pain — duloxetine, amitriptyline.
4. Motivational interviewing — behavior change (smoking, physical activity).

Source-specific specifications

• NICE CG91 — CBT for depression in cardiac patients.
• Levenson J.L. APA Textbook of Psychosomatic Medicine 2018.

Treatment methods

1. Consultation-Liaison Psychiatry — Integrated service in medical-surgical departments.
2. Cardiac CBT — Post-MI depression management.
3. Diabetes Self-Management Education (DSME) — Diabetes self-management training.
4. CBT and ACT for chronic pain — Williams Cochrane 2020.

9. Prognosis

Integrative approach improves both somatic and psychological outcomes.

10. Myths and misconceptions

Myth 1: “The illness is entirely psychological in origin”

Evidence: “Biopsychosocial” model — psychological factors influence but do not alone cause somatic illness.

Myth 2: “The psychiatrist is ‘running away’ from the illness”

Evidence: integrated approach — somatic and psychiatric intervention parallel.

Myth 3: “Alternative medicine (yoga, mindfulness) cures somatic illness”

Evidence: Complementary interventions may be adjunctive; does not replace standard somatic treatment (oncologic, cardiac).

Myth 4: “Telling the patient ‘you got sick because of stress’ is therapeutic”

Evidence: This approach undermines accusatory and therapeutic relationship.

11. Sources

1. WHO. ICD-11. 6E40 Psychological or behavioural factors affecting disorders or diseases classified elsewhere. 2024.
2. APA. DSM-5-TR. 2022.
3. Levenson J.L. (ed.). APA Publishing Textbook of Psychosomatic Medicine and Consultation-Liaison Psychiatry. 3rd ed. 2018.
4. NICE NG185. Acute coronary syndromes. 2020.
5. Whooley M.A., Wong J.M. Depression and cardiovascular disorders. Annu Rev Clin Psychol 2013;9:327–354.