Final Activity Report Summary - CTD_FAI_VALID (Validation of a Functional Assessment Interview Procedure for Childhood Tic Disorders) Although the neurobiological origins of tic disorders are well established, it is equally clear that actual tic expression is often sensitive to environmental factors. The reliable identification of these factors has considerable treatment implications; however, researchers suggest that the influence of any given factor is highly individualised. As a result, successful behavioural intervention requires the use of a flexible, yet valid method for identifying those environmental factors most relevant to a given individual. The goal of the current study was to investigate the influences of environmental factors on tic expression, while comparing objective and subjective assessments. 30 children and adolescents, aged 7-15, with Chronic Tic Disorder (including Tourette's Syndrome) participated in the study. Each subject completed a comprehensive diagnostic assessment, and went through a Functional Assessment Interview (FAI). The FAI is a semi-structured clinical interview, designed for identifying the personalized influences of environmental events on tic expression, focusing on five specific events: Being alone, watching T.V. doing homework, talking to an unfamiliar person, and getting attention for ticcing. At the next stage, the child was videotaped under these five conditions, twice each for the duration of ten minutes. The videotapes were scored for the number of tics, followed by a comparison of tic frequency between the various situations in relation to one another, and in relation to the FAI. Results show significant differences in tic frequency between the five situations, indicating that environmental factors do have individualized influences on tic expression. In addition, a correlation between tic frequency as observed on the videotapes and subject's report on the FAI was conducted, which was found significant only regarding one of these situations, suggesting that self-report may be unreliable. These findings contribute to a better understanding of the etiology and maintenance of tics, considering both neurological and psychological factors. Furthermore, they have important implications for the development and refinement of psychological treatments for tics, especially for planning behavioural interventions which are tailored to each patient and aim to minimise environmentally triggered tics.