Assessments of mental capacity in psychiatric inpatients: a retrospective cohort study

The Mental Capacity Act 2005 (MCA) was introduced in 2007 to protect vulnerable individuals who lack capacity to make decisions for themselves and to provide a legal framework for professionals to assess incapacity. The impact of the MCA on clinical practice is not known. This study aims to evaluate how frequently mental capacity is assessed in psychiatric inpatients, whether the criteria for determining capacity set out in the MCA are used in practice, and whether this has increased with the introduction of the MCA.

A retrospective cohort study was carried out using a case register of South East London mental health service users. The Case Register Interactive Search (CRIS) system enabled searching and retrieval of anonymised information on patients admitted to the South London and Maudsley NHS Foundation Trust since 2006. The presence and outcomes of documented mental capacity assessments in psychiatric admissions between May 2006 and February 2010 were identified and demographic information on all admissions was retrieved.

Capacity assessments were documented in 1,732/17,744 admissions (9.8%). There was a significant increase in the frequency of capacity assessments carried out over the study period of 0.3 percentage points per month (95% CI 0.26-0.36, p < 0.00001). In only 14.7% of capacity assessments were the MCA criteria for assessing capacity explicitly used.

Over the period of the introduction of the MCA there has been a significant increase in the number of mental capacity assessments carried out on psychiatric inpatients. Although mental health services are considering the issue of capacity more frequently, mental capacity assessments are inconsistently applied and do not make adequate use of MCA criteria.