A short writing exercise costing nothing and taking minutes a week. Mood improves reliably and sleep quality in most studies, though modestly and only while practice continues. Physical changes are thinner and uneven; in older women a grateful outlook tracked a slightly lower chance of dying, cause unproven. Harms appear minimal; it matches rather than beats structured positive-reflection practices. (Full Review)
| Marker | Target | Why |
|---|---|---|
| hs-CRP | <0.5 mg/L | Tracks the low-grade inflammation most often claimed as the physical benefit |
| Interleukin-6 | <1.5 pg/mL | The specific signalling protein altered in the one positive gratitude trial |
| Home blood pressure | 110–120 / 70–78 mmHg | The clinical surrogate with the clearest single-trial gratitude signal |
| Night-time HRV (rMSSD) | No established target for this intervention — track change from own baseline; a sustained fall beyond 10% across a month is the informative signal | Indexes the parasympathetic tone that rose acutely during journaling |
| PSQI global score | ≤5 | Sleep is the physical outcome with the most consistent gratitude signal |
| GQ-6 total | 36–42 of a possible 42 | Confirms the practice is shifting the target trait, not merely being performed |
| PHQ-9 total | ≤4 | Detects distress the practice is not addressing and that warrants established treatment |
| HbA1c | 4.8–5.4% (29–36 mmol/mol) | Relevant only where glucose control is the endpoint of interest |
| Morning salivary cortisol | 12–22 nmol/L on waking | Tests the stress-axis pathway most often proposed for gratitude |
Cadence: Questionnaires at baseline, 4 and 8 weeks; home blood pressure in seven-day blocks at baseline, week 4 and week 8; blood markers before the first session, again at 8–12 weeks, then every 6–12 months while practice continues; wearable heart rate variability read as a monthly trend.