Relational psychiatry takes an anti-mechanistic approach to life, including human life. Despite its attractions from Descartes onwards (see eg. previous post), a mechanistic conception of nature fails to provide a complete characterisation of living systems (see eg. another previous post). Medical psychology therefore needs to take a pragmatic anthropological approach as a mechanistic psychology is impossible to realise in practice. It needs to focus on the person-environment interaction.
The implications are that there is nothing else apart from the therapeutic relationship, both individual and group, in psychiatric treatment (although I agree with Richard that this position forms part of the definition of relational psychiatry, as it doesn't' necessarily follow from what I am saying about mechanistic psychology). I also agree with Richard that actual clinical practice is not necessarily the same as theoretical practice. Relational psychiatry does need to actually make psychiatry more relational. This means that practice needs to be truly person-centred (see eg. previous post). As Richard points out, the current Royal College of Psychiatrists' curriculum doesn't even make this clear.