Psychiatric Advance Directives (PADs) are documents that allow severe and chronic mentally ill users notifying preferences of treatment and appointing a surrogate decision-maker for crisis relapses. Despite many expected benefits at the intrapersonal, interpersonal and organisational levels of the mental health system, PADs take-up rate remains low and many barriers to their use were identified. Moreover, a recent Cochrane systematic review provided little evidence on these benefits.

A realist review was carried out to clarify the theoretical frameworks underlying PADs, examine data evidencing these frameworks and determine the conditions in which PADs may have an effect, on what issues, and how.

After a selection process, 38 references were retrieved from health and social sciences databases containing empirical data on PADs. Papers were thematically coded along identified theoretical frameworks and levels of effects, and populated with empirical data. Results were reported within a multistage process including the PAD definition, completion, registration, access, and honouring.

Three theoretical frameworks were identified: users' autonomy, therapeutic alliance and health providers' networking. Although PADs were set up in a user's autonomy approach, they produce better results within a therapeutic alliance framework. Networking is determining on access and honouring stages. However, the literature mainly focused on definition and completion stages. Very little is known about their actual honouring.

PAD is a complex intervention with effects and barriers at each step of the process and levels of action. Their take-up rate and evaluation could be improved assessing these levels and stages separately.