DASS 21 or PHQ 9 for Depression Monitoring in Routine Clinical Practice?

Vol 6 #4

Katherine Ramsden MD, Stephanie Waechter PhD, Alan Eppel MB, FRCPC



A quality improvement exercise was undertaken to determine whether the DASS 21 or PHQ 9 would be most useful in monitoring depression levels in patients with various diagnoses.


Both questionnaires were administered to 23 patients attending a hospital based psychiatric outpatient service. Patients in this setting have high levels of depression and the study was undertaken to determine the utility and comparability of these questionnaires for routine clinical practice.  Scores were compared using Pearson’s Correlation.


The Correlation between the two scores was 0.87.


Both of these instruments appear to measure the same construct. They have equal utility in  measuring severity of depressive symptoms in a hospital based outpatient facility.


In routine clinical practice it is helpful to monitor treatment response over time. This is most easily accomplished by using self-report questionnaires. To be effective these questionnaires should be relatively short and easy to complete, they should be validated and be in the public domain or available free of costs.

The Depression Anxiety and Stress Scales, 21 item version (DASS 21) has been validated for the rating of depressive and anxiety symptoms across multiple cultures (Lee et al).

The Patient Health Questionnaire 9 (PHQ 9) has also been validated, however, there has been some debate about choice of cutoff score (Manea et al 2017).

Both questionnaires have been shown to be sensitive to change in depression severity over time (Titov et al. Ng et al).

The DASS 21 and PHQ 9 have been compared with a number of other scales. In one early study the DASS 21 had a correlation coefficient with the Beck Depression Inventory of 0.79 (Antony et al). The correlation of the PHQ 9 with the Beck Depression Inventory has been determined in several studies (Choi et al. Kung et al. Smarr et al.) However the principal validity study of the PHQ 9 did not use the Beck Depression  or other primary measures of depression to test construct validity (Kruenke & Spitzer) This study was based on a large primary care patient population.

Studies of DASS 21 and PHQ 9 have been carried out on varied populations, both clinical and non-clinical and in varying settings. Therefore it cannot be assumed that the DASS 21 and the PHQ 9 are in fact comparable.


Both questionnaires were administered at the same visit to 23 patients attending a hospital- based psychiatric outpatient service. The patients were  not-selected group of outpatients.

The decision  to administer the scales was made at routine follow up visits by the same psychiatrist and/or same psychiatric resident. The scales were completed by patients who had prominent symptoms of depression regardless of diagnoses.

Twenty two patients scored at or above the threshold for  identification of depression on both instruments. The patients were 74% female. Age range was 25 to 70 yrs.  Diagnoses were mixed with complex problems: Major Depression with Anxiety, Major Depression with Psychosis, and combinations of Major Depression,  Posttraumatic Stress Disorder, Obsessive Compulsive Disorder, Generalized Anxiety Disorder, Social Anxiety Disorder and Substance Use Disorders.


The results are displayed in Table 1. A cut off score of 10 was chosen for PHQ 9 as lower scores may over-identify depression. DASS 21 score of 10 was also used .



ID # PHQ 9 DASS 21 Absolute Difference At/Above Cut off score of At/Above Cut off score of
10 on PHQ-9  10 on DASS
1 20 21 1 1 1
2 23 18 5 1 1
3 22 21 1 1 1
4 16 20 4 1 1
5 24 19 5 1 1
6 19 18 1 1 1
7 7 12 5 0 1
8 16 10 6 1 1
9 12 11 1 1 1
10 15 15 0 1 1
11 20 16 4 1 1
12 16 11 5 1 1
13 18 14 4 1 1
14 24 19 5 1 1
15 2 3 1 0 0
16 1 0 1 0 0
17 17 12 5 1 1
18 10 13 3 1 1
19 16 13 3 1 1
20 7 9 2 0 0
21 13 13 0 1 1
22 18 12 6 1 1
23 4 1 3 0 0
Number of scores above cut off 18 19
Pearson’s Correlation between PHQ 9 and DASS 21 scores = 0.87

Table 1


This study has demonstrated a high correlation between two measures in a real world clinical sample with comorbidity.  Both of these instruments appear to measure the same construct. They have equal utility in measuring severity of depressive symptoms in a hospital-based outpatient facility.


This was a QI study and does not meet the requirements for a research study. This was a small sample assessed during routine outpatient visits at one particular centre.

An area for further study is to assess how well the measures correlate when there is change in the levels of depression. Is one measure more sensitive to change than the other?

Disclosure Statement

No financial or other support was received for this project. None of the authors have any conflicts of interest.


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