Patient Health Questionnaire - 9 questions to measure depression
The PHQ-9 (external link) is the depression module of the PRIME-MD(external link) diagnostic instrument for common mental disorders that scores each of the 9 DSM-IV criteria as "0" (not at all) to "3" (nearly every day). It is designed to be self-administered. It generates five categories of depression based on a score between 0 and 27. A threshold score of 10 has a sensitivity and specificity of 88%(external link) for major depression.