His clinical research and practice has mainly focused on developing
cognitive models and
cognitive therapy for
anxiety disorders. His research has focused on
panic disorder,
hypochondriasis,
social phobia and
posttraumatic stress disorder. Clark was strongly influenced by the American
psychiatrist Aaron T. Beck who made long visits to Oxford University in the 70s and 80s, whose head of psychiatry
Michael Gelder strongly believed in cognitive therapy. Clark was instrumental, with the economist
Richard Layard, in the development and implementation of the
Improving Access to Psychological Therapies programme from 2003. In 2014, with Layard, he published the book
Thrive: The Power of Evidence-Based Psychological Therapies, in which the authors demonstrate the potential value of the wider availability of modern talking therapies. ==Personal life==