YHS AUDIT REPORT
YHS AUDIT PROCEDURE No 308i
Audit Date: 7.9.10
Previous Audit: 26.5.10
Title: Relationship between WEMWBS,
PHQ-9 & GAD-7 scores.
Page No 1 of 2
YHS Occasionally
Scope.
The analysis covers the determination of the relationship between all 3 test scores; the
Warwick-Edinburgh Mental Well-Being Scale 0 – 70 (WEMWBS), the General Anxiety
Disorder score 0 – 21 (GAD-7) and the Patient Health Questionnaire score 0 – 27 (PHQ-9).
The search found 955 patients with either a WEMWBS, a GAD-7 or a PHQ-9 score.
Of these, 242 patients have both WEMWBS & PHQ-9 scores; 184 have both WEMWBS &
GAD-7 scores; 213 have both GAD-7 & PHQ-9 scores and 172 with all three.
The sample size used for each comparison was 75 patients (not necessarily the same 75); there
is scope for ‘fine tuning’ the relationships by using larger sample sizes.
In the formulae below, WEMWBS is denoted by ‘W’, GAD-7 by ‘G’ & PHQ-9 by ‘P’.
Results.
 Relationship between WEMWBS scores and PHQ-9 scores.
70
60
WEMWBS
50
40
30
20
10
26
24
22
20
18
16
14
12
10
8
6
4
2
0
0
PHQ-9
Comments.
It will be seen that an inverse relationship exists between the WEMWBS scores and the PHQ-9
scores; the higher the WEMWBS score, the lower the PHQ-9 score for each patient. (An
inverse relationship will also be seen between the WEMWBS scores and the GAD-7 scores.
The mean WEMWBS score was 39.6 & the mean PHQ-9 score was 11.5.
The general relationship between a patient’s WEMWBS score & their PHQ-9 score is as the
following formula:
W = 54.82 – 1.254P
e.g. PHQ-9 score =11.5,
WEMWBS score = 54.82 – (11.5 x 1.254) = 54.82 – 14.42 = 40.4
The error when using this formula, and the other two formulae covering the other relationships,
for calculating equivalent scores is estimated at ± 2.5%.
08i10-11WEMWBS vGAD-7vPHQ-9
YHS AUDIT REPORT
YHS AUDIT PROCEDURE No 308i
Audit Date: 7.9.10
Previous Audit: 26.5.10
Title: Relationship between WEMWBS,
PHQ-9 & GAD-7 scores.
Page No 2 of 2
YHS Occasionally
Results (cont.)
 Relationship between WEMWBS scores & the GAD-7 scores.
70
60
WEMWBS
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21
GAD-7
Comments.
The mean WEMWBS score was 39.6 & the mean GAD-7 score was 11.0 (PHQ-9 was 11.5).
The general relationship between a patient’s WEMWBS score & their GAD-7 score is as the
following formula:
W = 51.83 – 1.114G.

Relationship between PHQ-9 scores & the GAD-7 scores.
27
24
21
PHQ-9
18
15
12
9
6
3
0
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21
GAD-7
Comments.
The mean GAD-7 score was 11.0 and the mean PHQ-9 score was 11.23.
The general relationship between a patient’s PHQ-9 score & their GAD-7 score is as the
formulae: P = 0.842G + 1.9701.
i.e. when G = 21, P = 19.7.
The relationship formulae derived from the two WEMWBS comparisons is:
P = 0.888G + 2.384.
i.e. when G = 21, P = 21.0.
Conclusion.
Although the PHQ-9 scale has a score up to 27 & the GAD-7 a score up to 21, this analysis
would indicate that both the PHQ-9 & the GAD-7 yield the same outcome & score. Calculating
χ2 between PHQ-9 of 19.7 & GAD-7 of 21.0 shows a probability of association of 99%.
08i10-11WEMWBS vGAD-7vPHQ-9