How much change is enough? Evidence from a longitudinal study on depression in UK primary care

Daphne-Zacharenia Kounali*, Katherine Button, Gemma Lewis, Simon Gilbody, David S Kessler, Ricardo Araya, Larisa Duffy, Paul Lanham, TJ Peters, Nicola J Wiles, Glyn Lewis

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

45 Citations (Scopus)
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The Patient Health Questionnaire (PHQ-9), the Beck Depression Inventory (BDI-II), and the Generalised Anxiety Disorder Assessment (GAD-7) are widely used in the evaluation of interventions for depression and anxiety. The smallest reduction in depressive symptoms that matters to patients is known as the Minimum Clinically Important Difference (MCID). Little empirical study of the MCID for these scales exists.


A prospective cohort of 400 patients in UK primary care were interviewed on four occasions, two weeks apart. At each time point, participants completed all three questionnaires and a ‘global rating of change’ scale (GRS). MCID estimation relied on estimated changes in symptoms according to reported improvement on the GRS scale, stratified by baseline severity on the Clinical Interview Schedule (CIS-R).


For moderate baseline severity, those who reported improvement on the GRS had a reduction of 21% (95% confidence interval (CI) -26.7, -14.9) on the PHQ-9; 23% (95% CI -27.8, -18.0) on the BDI-II and 26.8% (95% CI -33.5, -20.1) on the GAD-7. The corresponding threshold scores below which participants were more likely to report improvement were -1.7, -3.5 and -1.5 points on the PHQ-9, BDI-II and GAD-7, respectively. Patients with milder symptoms require much larger reductions as percentage of their baseline to endorse improvement.


An MCID representing 20% reduction of scores in these scales, is a useful guide for patients with moderately severe symptoms. If a treatment had the same effect on patients irrespective of baseline severity, those with low symptoms are unlikely to notice a benefit.
Original languageEnglish
Number of pages8
JournalPsychological Medicine
Early online date3 Nov 2020
Publication statusE-pub ahead of print - 3 Nov 2020


  • depression
  • primary care
  • BDI-II
  • PHQ-9
  • GAD-7
  • minimal clinically important difference
  • baseline severity
  • beta-regression


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