The nine-item Patient Health Questionnaire (PHQ-9) is a depressive symptom scale and diagnostic tool introduced in 2001 to screen adult patients in primary care settings. The instrument assesses for the presence and severity of depressive symptoms and a possible depressive disorder. The PHQ-9 is a component of the larger self-administered Patient Health Questionnaire (PHQ), but can be used as a stand-alone instrument. The PHQ is part of Pfizer's larger suite of trademarked products, called the Primary Care Evaluation of Mental Disorders (PRIME-MD). The PHQ-9 takes less than three minutes to complete. It is scored by simply adding up the individual items' scores. Each of the nine items reflects a DSM-5 symptom of depression. Primary care providers can use the PHQ-9 to screen for possible depression in patients. Source: Wikipedia (en)