APA Dictionary of Psychology

a widely used adult self-report depression-screening instrument designed to measure the intensity of depressive or mood-related symptoms. It is also a tool for tracking a client’s response to depression treatment over time. The SDS consists of 20 statements to which participants must respond using a 4-point Likert scale, ranging from none or little of the time to most or all of the time. Half of the questions are worded positively (e.g., “I have trouble sleeping”) and half are worded negatively (e.g., “I do not feel hopeful”). [originally developed in 1965 by William W. K. Zung, U.S. psychiatrist]