Are Equine Assisted Interactions (EAI) a Dark Horse Bet? A Systematic Review on Measuring the Psychological and Physiological Effects of EAI on PTSD, Anxiety and/or Mood Disorders. Background: Conventional forms of trauma-focused psychological interventions seem to be less effective in military veterans with post-traumatic stress disorder (PTSD). Equine Assisted Interventions (EAI) have become increasingly popular as an additional treatment, resulting in increasing research on the effects of EAI. However, no systematic review on the effects of EAI has focused on PTSD, anxiety and/or mood disorders and whether the effects are reflected in psychological and physiological measures. This systematic review investigated the treatment effects, study design, population, interven...