Mental capacity in psychiatric patients

Background Mental capacity is central to legal and ethical debates on the use of compulsion in psychiatry.

Aims To describe the clinical epidemiology of mental incapacity in patients with psychiatric disorders, including interrater reliability of assessments, frequency in the psychiatric population and associations of mental incapacity.

Method Cross-sectional studies of capacity to consent to treatment for psychiatric patients were systematically reviewed from Medline, EMBASE and PsycInfo databases. Information on the reliability of assessments, frequency and associations of mental incapacity was extracted.

Results Out of 37 papers reviewed, 29 different capacity assessment tools were identified. Studies were highly heterogeneous in their measurement and definitions of capacity. Interrater reliabilities between tools were high. Studies indicate incapacity is common (median 29%) but the majority of psychiatric in-patients are capable of making treatment decisions. Psychosis, severity of symptoms, involuntary admission and treatment refusal were the strongest risk factors for incapacity.

Conclusions Mental capacity can be reliably assessed. The majority of psychiatric in-patients have capacity, and socio-demographic variables do not have a major impact but clinical ones do.

Mental capacity is a multidimensional construct that is a central determinant of an individual’s ability to make autonomous decisions. Its assessment has become increasingly important with the move away from the paternalistic role of healthcare professionals towards a greater emphasis on an individual’s own treatment decisions (Schneider, 1998). The American Psychiatric Association has developed a model statute which uses a mental capacity test (Stromberg & Stone, 1983). In many other jurisdictions mental capacity and mental health legislation have developed along different lines to deal with the specific needs of different groups of patients. In both England and Scotland, mental capacity legislation has developed with the aim of providing a framework for people with either severe communication difficulties or cognitive problems (intellectual disability, dementia and other organic brain syndromes). In contrast, mental health legislation has developed with the needs of patients with psychiatric disorders – in particular, although not exclusively, psychotic disorders – in mind. Mental health legislation that does not use capacity tests generally applies a ‘status’ approach, whereby a wide range of treatments can be given to the patient on the basis of certain general conditions being met (e.g. the presence of a mental disorder, or the presence of perceived risk to the patient or others).

The use of status approaches has numerous implications. Under mental capacity legislation treatments are only provided in the patient’s best interests (with particular attention paid to previously expressed wishes, including advance directives, which have legal weight), whereas under mental health legislation best interests do not have to be considered, although in practice many psychiatrists effectively apply a best interests test . Further, the use of a ‘status’ approach means that the patient can be given a range of treatments, even if he or she might have capacity to refuse one or more of these. This has led some to suggest that current status-based approaches are anachronistic and unethical and that mental capacity and mental health legislation could be fused .