Construct: Depressive symptoms
Description of Measure: The PHQ-9 and PHQ-2, components of the longer Patient Health Questionnaire, offer psychologists concise, self-administered tools for assessing depression. They incorporate DSM-IV depression criteria with other leading major depressive symptoms into a brief self-report instruments that are commonly used for screening and diagnosis, as well as selecting and monitoring treatment.
The diagnostic validity of the 9-item PHQ-9 was established in studies involving 8 primary care and 7 obstetrical clinics. PHQ-9 scores > 10 had a sensitivity of 88% and a specificity of 88% for Major Depressive Disorder. Reliability and validity of the tool have indicated it has sound psychometric properties. Internal consistency of the PHQ-9 has been shown to be high. A study involving two different patient populations produced Cronbach alphas of .86 and .89. Criteria validity was established by conducting 580 structured interviews by a mental health professional. Results from these interviews showed that individuals who scored high (≥ 10) on the PHQ-9 were between 7 to 13.6 times more likely to be diagnosed with depression by the mental health professional. On the other hand, individuals scoring low (≤ 4) on the PHQ-9 had a less than a 1 in 25 chance of having depression (Kroenke et al, 2001).
The PHQ-9 also has been used in many studies in primary care settings, as well as with older individuals and with those who have physically disabling conditions. It is free to usersopens in new window and available in English and over 30 other languages.
The PHQ-2, comprising the first 2 items of the PHQ-9, inquires about the degree to which an individual has experienced depressed mood and anhedonia over the past two weeks. Its purpose is not to establish final diagnosis or to monitor depression severity, but rather to screen for depression. Patients who screen positive should be further evaluated with the PHQ-9 to determine whether they meet criteria for a depressive disorder. The PHQ-2 has been validated in 3 studies in which it showed wide variability in sensitivity (Gilbody, Richards, Brealey, and Hweitt, 2007).
References
Badr, H., Federman, A. D., Wolf, M., Revenson, T. A., & Wisnivesky, J. P. (2016). Depression in individuals with chronic obstructive pulmonary disease and their informal caregivers. Aging & Mental Health, 21(9), 975-982, doi: 10.1080/13607863.2016.1186153
Gilbody, S., Richards, D., Brealey, S., & Hewitt, C. (2007). Screening for depression in medical settings with the Patient Health Questionnaire (PHQ): A diagnostic meta-analysis. Journal of General Internal Medicine, 22(11), 1596-1602. 10.1007/s11606-007-0333-y
Kroenke K, Spitzer R L, Williams J B (2001). The PHQ-9: validity of a brief depression severity measure. Journal of General Internal Medicine, 16(9): 606-613.
Kroenke, K. & Spitzer, R.L. (2002). The PHQ-9: A new depression and diagnostic severity measure. Psychiatric Annals, 32, 509-521.