Coen Horstman works as a clinical psychologist/psychotherapist and a supervisor in Cognitive Behavioural Therapy and Schema Therapy. Since 2016 he has been working at the Vincent van Gogh Institute with patients with anxiety disorders, depression and personality disorders. From 2007-2016 he worked in the anxiety disorder and personality disorder team of the Riagg Maastricht. From 2007 onwards he has taken part in treatment studies regarding the effectiveness of Schema Therapy for Cluster C Personality Disorders and group Schema Therapy for Borderline Personality Disorder. During this period he was instructed by Jeffrey Young, Joan Farell, Ida Shaw, Arnoud Arntz and Hannie van Genderen.
Together with Hannie van Genderen, he was a group therapist with Group Schema Therapy for patients with Borderline Personality Disorder.
He has also had his independent practice in Roermond since 2011. There he treats patients with Schema Therapy and Cognitive Behavioural Therapy.