David A. Clark, PhD, is a clinical psychologist, and professor emeritus at the University of New Brunswick. He is author or coauthor of several books on depression, anxiety, and obsessive-compulsive disorder (OCD), including The Anxiety and Worry Workbook with Aaron T. Beck (founder of cognitive therapy), The Anxious Thoughts Workbook, The Negative Thoughts Workbook, and Cognitive-Behavioral Therapy for OCD and Its Subtypes. Clark is a founding fellow and trainer consultant with the Academy of Cognitive and Behavioral Therapies, and fellow of the Canadian Psychological Association. He is author of the blog, The Runaway Mind, on www.psychologytoday.com.