Operationalising the capability approach for outcome measurement in mental health research

Highlights

• Development and early applications of the OxCAP-MH capability instrument.

• Data collected for mental health service users involuntarily treated in hospital.

• Directly measuring human capabilities for the mentally ill is feasible.

• Capability scores significantly correlate with functioning and quality of life.

• Schizophrenia, female gender and longer illness duration have negative effects.

Abstract

Amartya Sen's multidimensional capability approach focuses on the importance of freedoms to be or do things people have reason to value. It is an alternative to standard utilitarian welfarism, the theoretical approach to quality-adjusted life years (QALYs) and cost-utility analyses. Despite the limitations of the utility approach in capturing non-health benefits and broader welfare inequalities, there have been very limited applications of the capability approach in the mental health context where these issues are imperative.

We report the development and application of a multidimensional instrument, the OxCAP-MH, which aims to operationalise the capability approach for outcome measurement in mental health research. The study was carried out as part of an ongoing programme on community coercion experienced by service users with severe and enduring mental illness being treated using Community Treatment Orders. Capabilities data were collected at baseline in the OCTET RCT for 333 ‘revolving door’ mental health service users who were in involuntary hospital treatment at the time of recruitment in England (2008–2011). The research focused on the identification of capabilities domains most affected by mental illness and their association with socio-demographic and clinical factors and other measures of well-being such as the EQ-5D and Global Assessment of Functioning (GAF) scales.

The OxCAP-MH item response rate was 90%–68%. There were significant correlations between service users' overall capability scores and the GAF, EQ-5D VAS and EQ-5D-3L utilities (corr = 0.249, 0.514, 0.415, respectively). The most affected capability domains were: ‘Daily activities’, ‘Influencing local decisions’, ‘Enjoying recreation’, ‘Planning one's life’ and ‘Discrimination’. Age had a mixed effect, while female service users and those with a primary diagnosis of schizophrenia or longer illness duration reported significantly lower capability scores. The results support the feasibility and validity of directly measuring human capabilities for the mentally ill and the potential for applying the approach to outcome measurement.

Introduction

Many people with severe and enduring mental illness experience significant social challenges. This may be due to stigma or discrimination, or to limitations to their freedom of choice and opportunities to enjoy social relationships, all of which may impact on their social participation, roles and opportunities for self-support. Current mental health services seek to address such issues by targeting both health and social impairments (Department of Health, 2009, Department of Health, 2011). As health and social care services for people with mental health problems have increasingly moved from institutions into the community, the planning, financing, provision and evaluation of services have become multi-layered and complex.

The latest guidance by the UK National Institute for Health and Care Excellence (NICE) advocates the adoption of a joint health and social care perspective when measuring costs in evaluations, and highlights the importance of distributive considerations when developing recommendations. As the preferred outcome measure for decision making, NICE supports Quality Adjusted Life Years (QALYs) and the use of the EQ-5D – a generic, multi-attribute health status classification scale commonly used for QALY calculations – to develop utility weights (The EuroQol Group, 1990, National Institute for Health and Clinical Excellence, 2008). A QALY is a unit that combines both quantity (length) of life and health-related quality of life into a single measure of health gain. Health-related quality of life is anchored on a 0–1 utility scale with ‘0’ being the value of ‘dead’ and ‘1’ being the value of ‘perfect health’ (Drummond, Sculpher, Torrance, O'Brien & Stoddart, 2005). In their current form, QALYs have limited ability to capture non-health effects, and may be insensitive to the impact of social care interventions and so underestimate the full welfare impact of mental health interventions (Francis & Byford, 2011). Some concerns have also emerged about the fitness of the EQ-5D, when administered to people with psychotic or severe and complex nonpsychotic mental disorders (Brazier, 2010).

The objective of this paper is to present the development and application of the OxCAP-MH instrument that is part of a wider programme of work to use the capability approach for alternative outcome measurement in mental health research. The first part of this paper provides a theoretical background to the capability approach in the context of health. The second part of the paper reports the methods used in the development and early application of a multidimensional instrument, the OxCAP-MH. The third part presents the baseline findings on social functioning, health-related quality of life and capabilities amongst participants in the Oxford Community Treatment order Evaluation Trial (OCTET) (Burns et al., 2010, Burns et al., 2013). The final section discusses the findings and contrasts the current application with other recent attempts to operationalise the capability approach in the health and social care context.