Participants
DISORDER
The study population consisted of patients suffering from substance use disorder receiving their care at Behman Hospital during the time of the study. The inclusion criteria were being adult diagnosed with substance use disorder, hospitalized for at least one month in the study hospital, and physically able to deal with horses. Those patients suffering from any other physical or psychological ailments preventing them from active participation in the intervention were excluded. Using the G*Power sample size software program, the required sample size per group was 50 to detect scores’ improvement with a medium effect size (0.60) at 95% level of confidence and 80% power accounting for an expected dropout rate of about 20%. A total of 150 patients were enrolled, of which 30 were excluded for not meeting the eligibility criteria, and 20 for refusing participation (Fig. 
The flowchart of the study