The Patient Health Questionnaire (PHQ) is a multiple-choice self-report inventory that is used as a screening and diagnostic tool for mental health disorders of depression, anxiety, alcohol, eating, and somatoform disorders. It is the self-report version of the Primary Care Evaluation of Mental Disorders (PRIME-MD), a diagnostic tool developed in the mid-1990s by Pfizer. The length of the original assessment limited its feasibility; consequently, a shorter version, consisting of 11 multi-part questions – the Patient Health Questionnaire was developed and validated.
In addition to the PHQ, a nine-item version to assess symptoms of depression, a seven-item version to assess symptoms of anxiety (GAD-7) and a 15-item version to detect somatic symptoms (PHQ-15), have been developed and validated. The PHQ-9, GAD-7, and the PHQ-15 were combined to create the PHQ-somatic, anxiety, depressive symptoms (PHQ-SADS) and includes questions regarding panic attacks (after the GAD-7 section). Though less commonly used, there are also brief versions of the PHQ-9 and GAD-7 that may be useful as screening tools in some settings. In recent years, the PHQ-9 has been validated for use in adolescents, and a version for adolescents was also developed and validated (PHQ-A). Although these tests were originally designed as self-report inventories they can also be administered by trained health care practitioners.
The PHQ is available in over 20 languages, available on the PHQ website. Both the original Patient Health Questionnaire and later variants are public domain resources; no fees or permissions are required for using or copying the measures. Additionally, the measures have been validated in a number of different populations internationally.
Versions The original Patient Health Questionnaire contains five modules; these contain questions about depressive, anxiety, somatoform, alcohol, and eating disorders. Designed for use in the primary care setting, it lacks coverage for disorders seen in psychiatric settings. Some modules are used independently, and variants have been developed based on the original items.
9-item depression scale
The PHQ-9 (DEP-9 in some sources), a tool specific to depression, scores each of the 9 DSM-IV related criteria based on the mood module from the original PRIME-MD. The PHQ-9 is both sensitive and specific in its diagnoses, which has led to its prominence in the primary care setting. This tool is used in a variety of different contexts, including clinical settings across the United States as well as research studies.
One study which used the PHQ-9, examined if college student displays of depression symptoms on Facebook were representative of offline symptoms. Results demonstrated that those who displayed depression symptoms on Facebook scored higher on the PHQ-9, suggesting that those who display depression symptoms on Facebook are experiencing them offline.
2-item depression screener
The Patient Health Questionnaire 2 item (PHQ-2) is an ultra-brief screening instrument containing the first two questions from the PHQ-9. Two screening questions to assess the presence of a depressed mood and a loss of interest or pleasure in routine activities, and a positive response to either question indicates further testing is required. This version of the PHQ has been shown to have good diagnostic sensitivity but poor specificity.
4-item depression and anxiety screener
The Patient Health Questionnaire 4 item (PHQ-4) combines the PHQ-2 with the Generalized Anxiety Disorder 2 (GAD-2), an ultra-brief anxiety screener containing the first two questions from the Generalized Anxiety Disorder 7 (GAD-7).
15-item somatic scale
The Patient Health Questionnaire 15 item (PHQ-15) contains the PHQ's somatic symptom scale. It is a well-validated measure, which asks whether symptoms are present and about their severity. A brief version, the Somatic Symptom Scale – 8, was derived from PHQ-15. The development of the PHQ-15 helped address three main problems in the assessment and diagnosis of somatoform disorders. Firstly, traditional methods of diagnosing somatoform disorders would only capture about 20% of true cases due to the number of symptoms required to meet a diagnosis. Secondly, in order to attain more reliable and valid data, assessments need to address more current rather than previous symptoms. Thirdly, continuing to adhere to the "medically unexplained" requirement for symptoms makes it very difficult to make a diagnosis because it is extremely hard to ascertain if a symptom is or is not part of a larger medical condition (e.g. chronic fatigue and depression).
7-item anxiety scale
The GAD-7 is a 7-item scale designed to assess symptoms of anxiety. Each item is scored on a 0-to-3 point scale ("not at all" to "nearly every day"). Cut points of 5, 10, and 15 correspond to mild, moderate, and severe anxiety.
8-item depression scale The PHQ-8 is an eight-item scale developed specifically to screen for depression in American epidemiological populations.
Somatic, anxiety, and depressive symptoms
The Patient Health Questionnaire – Somatic, Anxiety, and Depressive Symptoms (PHQ-SADS) screens for somatic, anxiety, and depressive symptoms using PHQ-9, GAD-7, and PHQ-15, plus the panic symptoms question from the original PHQ.
Adolescent scale The PHQ-A is a four module self-report to evaluate depression, anxiety, substance use and eating disorders in adolescent primary care patients.
Reliability Measure Criterion Rating* (adequate, good, excellent, too good) ExplanationPHQNormsExcellentMultiple convenience and random samples, as well as research studies in both clinical and nonclinical sample Internal consistency (Cronbach's alpha, split half, etc.)GoodCronbach's alpha reported at .88 for measuring depressionInter-rater reliabilityGoodKappas range from .64 to .81 for depression. Kappa for anxiety is .83Test-retest reliability (stability) No published studies formally checking test-retest reliabilityRepeatability No published studies formally checking repeatabilityPHQ-9NormsExcellentMultiple convenience and random samples, as well as research studies in both clinical and nonclinical samples. Internal consistency (Cronbach's alpha, split half, etc.)GoodCronbach's alphas range from .83 to .89Inter-rater reliabilityGoodOne study in Nigerian university students with found ranges between .83 and .92Test-retest reliability (stability)AdequateCorrelation between administrations done within 48 hours was .84.RepeatabilityNot publishedNo published studies formally checking repeatability.GAD-7NormsExcellentMultiple convenience and random samples, as well as research studies in both clinical and nonclinical samples Internal consistency (Cronbach's alpha, split half, etc.)GoodCronbach's alpha reported at .92Inter-rater reliabilityGoodThe interviewer vs. self-rated correlation ranges from .83 and .84Test-retest reliability (stabilityGoodReported as .83RepeatabilityNot publishedNo published studies formally checking repeatabilityPHQ-15NormsExcellentTwo large studies with convenience and random samples used. One research studies (N=906) in clinical sample and one research study (N=6000) in nonclinical sample. Internal consistency (Cronbach's alpha, split half, etc.)GoodCronbach's alpha reported at .80Inter-rater reliabilityNo published studies formally checking inter-rater reliabilityTest-retest reliability (stability)GoodKappa = .60 when administration was done within 2 weeks of first testRepeatability No published studies formally checking repeatability.
Validity Measure Criterion Rating* (adequate, good, excellent, too good*) Explanation with references PHQContent validityGoodCovers DSM-IV criteria for major depressive disorder, panic disorder, other anxiety disorder, bulimia nervosa, other depressive disorder, probable alcohol abuse or dependence, and somatoform and binge eating disordersConstruct validity (e.g., predictive, concurrent, convergent, and discriminant validity)AdequateConstruct validity has not been fully established, and more substantial evidence of convergent and discriminant validity would be helpful. Validity is consistent with PRIME-MD.Discriminative validityExcellentAUCs range from .89 to .92 for detecting depressionValidity generalization No published studies formally checking validity generalization.Treatment sensitivity No published studies formally checking treatment sensitivity.Clinical utilityGoodThe PHQ is free and can be completed independently by the patient; it assesses a wide array of mental health concerns. PHQ-9Content validityExcellentCovers the DSM-IV criteria for major depressive disorder.Construct validity (e.g., predictive, concurrent, convergent, and discriminant validity)GoodHigher PHQ-9 scores were correlated with greater self-reported disability days, clinic visits, health-care utilization, as well as difficulties in activities and relationships.Discriminative validityToo excellentAn average sensitivity of .77 and specificity of .94 (corresponding to an AUC .94) in primary care settings suggests good discriminative validity in populations that are generally not depressed, but it may not perform as well in clinical populations. Validity generalizationVariableA meta-analysis of 27 samples suggested that performance of the PHQ-9 is highly heterogeneous; pooled sensitivity is low and specificity is high.Treatment sensitivityGoodIn a treatment study using three medical outpatient cohorts, the PHQ-9 has been shown to be sensitive to change over time
The PHQ-9 has been used in studies to effectively monitor change following cognitive behavioral treatment.