OPEN MINDS The Behavioral Health & Social Service Industry Analyst Industry Statistic Median length of stay (MLOS) for behavioral health treatment varies significantly by type of hospital, according to a study by OPEN MINDS. An analysis of unpublished NIMH data, from 1980 to 1986, revealed that 16 days is the MLOS for the inpatient treatment of mental illness and chemical dependency for all patients in all types of hospitals. The inpatient behavioral health MLOS varies from 27 days in state and county hospitals; to 24 days in private psychiatric . . .