Advice

Final diagnosis should be made with clinical interview and mental status examination including assessment of patient’s level of distress and functional impairment.

Management

Score	Depression Severity	Comments
0-4	Minimal or None	Monitor; may not require treatment
5-9	Mild	Use clinical judgment (symptom duration, functional impairment) to determine necessity of treatment
10-14	Moderate	Use clinical judgment (symptom duration, functional impairment) to determine necessity of treatment
15-19	Moderately Severe	Warrants active treatment with psychotherapy, medication, or both
20-27	Severe	Warrants active treatment with psychotherapy, medication, or both

Action

Perform suicide risk assessment in patients who respond positively to item 9 “Thoughts that you would be better off dead or of hurting yourself in some way.”
Rule out bipolar disorder, normal bereavement, and medical disorders causing depression.

Fact

The PHQ-9 is a validated, 9-question tool to assess for the degree of depression present in an individual; the last question is not scored, but is useful functionally to help the clinician assess the impact of the patient's symptoms on his or her life.

Evidence

The PHQ-9 was initially developed by Kroenke et al (2001), as a subset of 9 questions from the full PHQ, which had previously been derived and studied in a cohort of 6,000 patients in 8 primary care clinics and 7 obstetrics-gynecology clinics (Spitzer 1999). PHQ-9 scores ≥10 were found to be 88% sensitive and also 88% specific for detecting Major Depressive Disorder (MDD). Criterion validity was also assessed in a sample of 580 patients.
Arroll et al (2010) validated the PHQ-9 as a screener for MDD in a cohort of 2,642 primary care patients and found slightly higher specificity (91%) and lower sensitivity (74%) at the same cutoff of 10 points.
The PHQ-9 has also been validated in several additional subpopulations, including in psychiatric patients (Beard 2016), patients with medical comorbidities such as Parkinson’s disease (Chagas 2013), pregnant patients (Sidebottom 2012), and in an occupational health setting (Volker 2016).
A meta-analysis of 29 studies including 6,725 patients found similar sensitivity (88%, 95% CI 83-92%) and specificity (85%, 95% CI 82-88%) for a cutoff of ≥10 as did the previous studies, both overall and for subgroups. Notably, they found that when used in the primary care setting, only approximately 50% of patients screening positive on the PHQ-9 in fact had major depression (Levis 2019).

Use

To assist the clinician in making the diagnosis of depression.
To quantify depression symptoms and monitor severity.
Objectively determines severity of initial symptoms, and also monitors symptom changes and treatment effects over time.

Pearls/Pitfalls

The PHQ-9 is the MDD module of the full PHQ.
Used to provisionally diagnose depression and grade severity of symptoms in general medical and mental health settings.
Scores each of the 9 DSM criteria of MDD as “0” (not at all) to “3” (nearly every day), providing a 0-27 severity score.
The last item (“How difficult have these problems made it for you to do your work, take care of things at home, or get along with other people?”) is not included in score, but is a good indicator of the patient’s global impairment and can be used to track treatment response.
Higher PHQ-9 scores are associated with decreased functional status and increased symptom-related difficulties, sick days, and healthcare utilization.
May have high false-positive rates in primary care settings specifically (one meta-analysis found that only 50% of patients screening positive actually had major depression) (Levis 2019).

Reference

Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606-613. doi:10.1046/j.1525-1497.2001.016009606.x
Spitzer RL, Kroenke K, Williams JB. Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. Primary Care Evaluation of Mental Disorders. Patient Health Questionnaire. JAMA. 1999;282(18):1737-1744. doi:10.1001/jama.282.18.1737
Arroll B, Goodyear-Smith F, Crengle S, et al. Validation of PHQ-2 and PHQ-9 to screen for major depression in the primary care population. Ann Fam Med. 2010;8(4):348-353. doi:10.1370/afm.1139
Beard C, Hsu KJ, Rifkin LS, Busch AB, Björgvinsson T. Validation of the PHQ-9 in a psychiatric sample. J Affect Disord. 2016;193:267-273. doi:10.1016/j.jad.2015.12.075
Chagas MH, Tumas V, Rodrigues GR, et al. Validation and internal consistency of Patient Health Questionnaire-9 for major depression in Parkinson's disease. Age Ageing. 2013;42(5):645-649. doi:10.1093/ageing/aft065
Sidebottom AC, Harrison PA, Godecker A, Kim H. Validation of the Patient Health Questionnaire (PHQ)-9 for prenatal depression screening. Arch Womens Ment Health. 2012;15(5):367-374. doi:10.1007/s00737-012-0295-x
Volker D, Zijlstra-Vlasveld MC, Brouwers EP, Homans WA, Emons WH, van der Feltz-Cornelis CM. Validation of the Patient Health Questionnaire-9 for Major Depressive Disorder in the Occupational Health Setting. J Occup Rehabil. 2016;26(2):237-244. doi:10.1007/s10926-015-9607-0
Levis B, Benedetti A, Thombs BD; DEPRESsion Screening Data (DEPRESSD) Collaboration. Accuracy of Patient Health Questionnaire-9 (PHQ-9) for screening to detect major depression: individual participant data meta-analysis [published correction appears in BMJ. 2019 Apr 12;365:l1781]. BMJ. 2019;365:l1476. Published 2019 Apr 9. doi:10.1136/bmj.l1476