Clinicians often prescribe depot medication assuming that it will improve medication adherence. Few studies have systematically explored patterns of non-adherence with depots or whether the beliefs and attitudes that influence adherence are similar to those that affect acceptability and adherence of oral medication.

To investigate adherence with and attitudes towards depot medication.

1. (1) To explore non-adherence with depot medication.

2. (2) To examine key determinants of acceptability of depot versus oral treatment.

Patients with a severe mental disorder receiving depot medication completed a face to face interview incorporating several ratings, including the Beliefs about Medication Questionnaire (BMQ). Frequency of depot injections and adherence rates were recorded over two years. Data were compared with that from similar patients receiving oral medication.

Full adherence with depots was only slightly higher than with oral medication (77% v 71%). Although side effect ratings were correlated with the BMQ-Concerns sub-scale (r.29) the most robust single predictor of adherence was a high score on the BMQ Necessity scale (r .46). In both oral and depot medication groups the combination of Low Necessity and High Concerns predicted poor adherence (Odds Ratio 4.21).

Depot medication is a necessary but not sufficient treatment for many non-adherent patients. Our findings suggest that barriers to acceptance of depots vary little from those that impair adherence with oral antipsychotics and that interventions to modify these beliefs are as important as the mode of delivery of treatment.