Capacity to consent to treatment in psychiatry inpatients - a systematic review.

Background: Mental capacity for treatment decisions in psychiatry inpatients is an important ethical and legal concern, especially in light of changes in mental capacity legislation in many jurisdictions.

Aims: To conduct a systematic review of literature examining the prevalence of mental capacity for treatment decisions among voluntary and involuntary psychiatry inpatients, and to assess any correlations between research tools used to measure mental capacity and binary judgements using criteria such as those in capacity legislation.

Method: We searched PsycINFO, Ovid MEDLINE and EMBASE for studies assessing mental capacity for treatment decisions in people admitted voluntarily and involuntarily to psychiatric hospitals.

Results: Forty-five papers emanating from 33 studies were identified. There was huge variability in study methods and often selective populations, but the prevalence of decision-making capacity varied between 5% and 83.7%. These figures resulted from studies using cut-off scores or categorical criteria only. The prevalence of decision-making capacity among involuntary patients ranged from 7.7% to 42%, and among voluntary patients ranged from 29% to 97.9%. Two papers showed positive correlations between clinicians' judgement of decision-making capacity and scores on the MacArthur Competence Assessment Tool for Treatment; two papers showed no such correlation.

Conclusions: Not all voluntary psychiatry inpatients possess mental capacity and many involuntary patients do. This paradox needs to be clarified and resolved in mental health legislation; supported decision-making can help with this task.Key PointsLegislative changes for mental capacity are taking place in many jurisdictions.This is an important human rights issue for many people, including psychiatry inpatients.In our review, we found the prevalence of decision-making capacity varies between 5% and 83.7% in psychiatry inpatients.Not all voluntary inpatients have decision-making capacity.Many involuntary inpatients have mental capacity to make decisions.Supported decision-making can help those with impairments in their mental capacity.