BackgroundDue to long waiting periods for outpatient psychotherapy and the high resource requirements of inpatient treatment, there is a need for alternative treatment programs for patients with depressive disorders. Thus, we investigated the effectiveness of the “Bielefeld Outpatient Intensive Treatment Program of Depression” (BID) in comparison with a typical inpatient treatment program by using a prospective quasi-experimental observational study. We assumed (i) that both complex programs are effective in pre-post analyses after 6 weeks and (ii) that inpatient treatment is more effective compared with the outpatient program.MethodsFour hundred patients with depressive psychopathology – a majority with depressive episodes (ICD-10 F3X) - took part in the BID and 193 in the inpatient program. Different self- (i.e., BDI) and expert measures (i.e., MADRS) of psychopathology at baseline (t1) and 6 weeks later (t2) were applied to examine treatment effects.ResultsTreatment effects were high in separate analyses of both groups with Cohen’s d ranging from 1.10 to 1.76., while ANOVA comparative analyses did not reveal any significant differences between both treatment settings nor did a set of independent covariates analyzed here. Response rates of BDI (p = .002) and MADRS (p = .001) were higher in the outpatient group. Results indicate BID not to be inferior compared to an inpatient program, although diverging pathways to treatment, higher rates of clinical recurrent depressive disorders and severe episodes as well as lower rates of employment and partnership in the inpatient treatment group have to be considered.ConclusionOutpatient intensive treatment programs may represent a solution for patients needing more than a treatment session once per week but less than a complex inpatient or day clinic program.