Sarah Cassidy is an educational, child and adolescent psychologist who specialises in the assessment and treatment of learning and emotional/behavioural difficulties. She is the Founder and Director of the Smithsfield Clinic, a private practice for young people and their families using largely ACT (Acceptance and Commitment Therapy) and RFT (Relational Frame Theory) treatment methods. She lectures in Psychology at Maynooth University and trains ACT therapists throughout Ireland.