Chronic pain × depression comorbidity — 50% of Korea's 22% chronic-pain population also depressed, integrated SNRI treatment 12 weeks

Chronic pain — Korea's hidden depression

Chronic pain = pain lasting 3+ months. 22% Korean adults, OECD average 19%, US 20% — slightly higher in Korea. Common types: chronic low back pain (8%), migraine (12%), fibromyalgia (3%), arthritis (15% in ≥65s). Yet 50% of chronic-pain patients have comorbid depression / anxiety — frequently missed by Korean doctors. "Pain = body", "depression = mind" separation in clinical practice is the problem.

Bidirectional causality

Pain → depression: 24/7 pain, no sleep, no exercise, no social activity → helplessness, isolation, depression. After 6 months of chronic pain, depression-onset risk 4×.

Depression → pain: depressed patients have heightened pain sensitivity (central sensitization). Stronger pain perception for same stimulus. 65% of depressed patients report somatic pain (back, headache, abdomen, muscle).

Usually bidirectional simultaneously. Hard to tell which came first.

Shared neural mechanism

Recent neuroscience: chronic pain and depression share the same brain circuits (amygdala, anterior cingulate, thalamus). Serotonin, norepinephrine, dopamine all act on both pain and depression. Neurological basis for one drug (SNRI) improving both. "Pain" and "depression" may be different expressions of the same disorder.

Diagnostic traps in Korean healthcare

• Pain clinic doesn't refer to psychiatry ("me, psychiatry?")
• Psychiatry ignores pain ("pain belongs to a different specialty")
• "Doctor shopping" 6 months ~ 3 years
• Ends in "nothing found" / "functional" diagnosis → no medication, no treatment
• Opioid dependency risk

Solution: pain clinic (anesthesiology / rehabilitation medicine) + psychiatry collaborative care. "Pain-mental health clinics" at tertiary hospitals.

First-line pharmacotherapy

SNRI (Serotonin-Norepinephrine Reuptake Inhibitor)

• Duloxetine (Cymbalta): FDA-approved for chronic low back pain, fibromyalgia, diabetic neuropathy, depression. 60 mg/day. 12-week effect.
• Venlafaxine (Effexor): duloxetine alternative. Depression + chronic pain.

Note: SSRIs (Zoloft, Lexapro) treat depression only, weak on pain. Chronic pain comorbidity = SNRI first-line.

Tricyclics (TCA): low-dose amitriptyline (25~50 mg) — neuropathic pain, migraine prophylaxis. Lower than depression dose (150~300 mg). Watch for side effects (drowsiness, dry mouth).

Opioids — last resort: tramadol, morphine. ≥4 weeks of use risks dependency, tolerance, worsened depression. Concerning increase in Korean opioid prescriptions. Recommend 1-month cap.

CBT-CP 12-week protocol

Weeks 1~4 pain education and graded activity: restructure "pain = damage signal" perception — chronic pain is "neural hypersensitivity" rather than "injury". Daily activity log, gradual increase (5%/week).

Weeks 5~8 cognitive restructuring: "this pain disables me for life" → "pain ≠ damage, activity possible with pain". Challenge catastrophizing. Work depression cognitions concurrently.

Weeks 9~12 pacing: activity ↔ rest balance. From "pain-free day → all activities" to "50% even on pain-free days". Reduces flare-ups.

Korean pain clinic / clinical psychology 12 weeks ₩1.0~2.0M. Partial insurance.

Exercise prescription — analgesic-grade effect

Meta-analyses: effect size of exercise for chronic low back pain (Cohen's d) = 0.3~0.5, equivalent to NSAIDs. Also d=0.4 for depression (equal to SSRIs). "Exercise = analgesic + antidepressant".

• Swimming: 3×/week, 30 min. Zero-gravity = no joint load.
• Yoga: 3×/week, 60 min. First-line recommended for chronic low back pain, fibromyalgia.
• Walking: 30 min daily, 5,000~7,000 steps. OK even with knee arthritis.

First 2 weeks pain may rise, then decline. Gradual increase is key.

6 self-protection strategies

1. Simultaneous pain + depression dx: PHQ-9 + pain VAS scale on same day. Screen all chronic-pain patients for depression.
2. SNRI first-line: at pain clinic, mention "with depression" → SNRI prescription suggested.
3. Exercise prescription: swimming, yoga 3×/week. Common refusal of exercise with pain → gradual start.
4. Opioid 1-month cap: tramadol >1 month = re-evaluate at psychiatry / pain clinic. Respond immediately to dependency signals (dose escalation, earlier dosing, withdrawal on cessation).
5. Social reintegration: chronic-pain patient social avoidance → vicious cycle of more depression and pain sensitivity. Maintain 50% social activity even with pain.
6. Sleep priority: 70% of chronic-pain patients have sleep disorder. Pain → no sleep → ↑depression and pain sensitivity vicious cycle. Sleep hygiene + trazodone if needed.

Warning signs — immediate help

• "Endless pain, better to die" thought
• Escalating opioid use, multiple-prescriber shopping
• Alcohol + analgesic combined (liver / respiration risk)
• Halted all activity, not leaving bed
• Cut off all family communication

Chronic pain suicide risk = 2× general population. 1577-0199 or ER immediately.