background   Currently, no empirical data are available concerning the effectiveness of treatment provided by institutions based on particular religious or philosophical principles (e.g. Christian or anthroposophical clinics and clinics providing 'culture-sensitive' treatment). This is regrettable because these institutions claim that they achieve excellent results.

aim   To obtain more insight into the effectiveness of treatment (and the drop-out rate) at clinics based on specific religious and philosophical principles and to compare their results with the results of treatment at a regular clinic.

method   In this prospective study data were collected for 182 in-patients admitted to 4 different clinics providing addiction treatment; one provides regular treatment and two provide culture-sensitive treatment and one anthroposophical treatment respectively. By means of regression analysis we investigated whether there were significant differences in the drop-out rate at the three clinics concerned. Thereafter we performed a second analysis correcting for potential confounders (baseline variables that were significantly different for the 3 patient groups).

results   The most important finding was that in the first phase of treatment the drop-out figures at the clinics did not differ significantly. However, we were surprised to find that the late drop-out figures in the units for continuation treatment at the anthroposophical clinical Arta were considerably lower than the late drop-out figures at the regular clinic Centrum Maliebaan.

discussion   Clinics based on particular religious or philosophical principles (such as Arta) may be able to keep patients in treatment for longer periods than regular clinics (such as Centrum Maliebaan). The difference is probably due partly to selection, Arta admitting relatively large numbers of patients who are strongly motivated to participate in continuation treatment. Other possible reasons for the difference are patient-centred treatment, programme cohesion and programme structure, continuity of care, and the policy of strengthening the healthy and positive elements of the patient's condition.