A screening tool that measures behavior in children over the last month to six months. The SDQ is available in various versions—a One-Sided, Informant-Rated version for parents and teachers, which is completed by parents and teachers of children aged 4 to 16 years; a One-Sided, Informant-Rated Parent and Teacher version for completion by parents and teachers of children aged 3 to 4 years (identical to the parent/teacher version for 4 to 16 year-olds except for three age-modified questions); and a One-Sided, Self-Rated version for adolescents aged 11 to 16 years. Each version consists of 25 items that measure positive and negative attributes based on five sub-scales—Emotional (5 items), Conduct (5 items), Hyperactivity/Inattention (5 items), Peer Relationship Problems, and Prosocial Behavior. Double-sided SDQ versions are also available in all of the One-Sided versions. The Double-Sided SDQ versions consist of a front side containing the primary 25 questions, but also contain a back side, called an Impact Supplement, that allows for further elaboration of behavior. Additionally, there is a Follow-up version of the SDQ, which includes the original 25 items and the Impact Supplement, but also two extra questions that inquire about treatment effectiveness. Contrary to the other SDQ versions, which measure a child’s behavior over the past six months and/or the current school year, the Follow-up version only assesses behavior over the past month. Response options for the 25 items on all versions are based on a 3-point scale—Not True, Somewhat True, and Certainly True. Response options for the Impact Supplement for all versions are—Not at All (0), Only a Little (0), Quite a Lot (1), and A Great Deal (2). Impact Scores range from 0 to 10, with scores of two or more considered abnormal. The five sub-scales generate an overall SDQ score, which ranges from 0 to 40, with scores between 20 and 40 indicative of abnormal behavior. Individual scores for each of the five sub-scales can also be calculated