The objective of the study is to assess the impact of horse assisted therapy (HAT) on:

• Addiction treatment outcomes (its effectiveness as an alternative therapy)
• Addiction treatment dropout & addiction relapse (its efficacy in preventing dropout).

Hypothesis: HAT will correlate with:

• beneficial treatment outcomes of depression, anxiety, aggression
• with improved self esteem & motivation
• lower treatment dropout & addiction relapse.

Background Inclusion of horses in therapeutic settings is a scientific issue with significant social and health implications in Norway. Challenges include increasing provision of horse assisted therapy of variable quality to vulnerable population groups with little substantiating evidence of associated benefit(s) due to lack of research, design issues, mainstream clinicians'/scientists' scepticism of "alternative therapy" and associated difficulties in attracting top researchers and funding. Extensive review of literature found a growing volume of studies but as indicated in the most recent systematic review, there are few studies with adequate research design.

Oslo University Hospital's Dept of Addiction Treatment - Youth (AUA) presents a unique research/evaluation potential to study HAT. It will treat approximately 100 patients per year aged 16 to 26 years with a primary diagnosis of addiction. Horse assisted therapy (using AUA's residential herd) is an integral part of the addiction therapeutic program. Furthermore, AUA's strong emphasis on research and its Youth Addiction Treatment Evaluation Project (YATEP) data base will provide an evidence base needed for sound study in an emerging area of science and psychotherapy.

Patient drop out from addiction therapy is high, often exceeding 50% (Stark 1992). Many AUA patients claim that they remain in treatment because of the horses.

The study is a randomised controlled trial of in-patients undergoing treatment. The Participant Group has treatment as usual plus HAT; the Control Group treatment as usual.

Participant and control groups are drawn from AUA patients (aged 16 to 26 years of age with a primary diagnosis of addiction International Classification of Diseases (ICD F10-F19), admitted between 2013 and 2014 to AUA's in-patient unit and who have consented to participate in research.

HAT is a structured program of 12 X 90 minute therapeutic sessions with horses, including horse care, ground and mounted work, conducted by two clinically qualified therapists who are also Level I Riding Instructors.

Inclusion Criteria:

• Primary diagnosis of addictionInternational Classification of Diseases ICD F10-F19, admitted in 2011-2014 for treatment at AUA's in-patient unit

Exclusion Criteria:

• Ongoing psychoses