Is the nature of decision-making capacity (DMC) for treatment significantly different in medical and psychiatric patients?

To compare the abilities relevant to DMC for treatment in medical and psychiatric patients who are able to communicate a treatment choice.

A secondary analysis of two cross-sectional studies of consecutive admissions: 125 to a psychiatric hospital and 164 to a medical hospital. The MacArthur Competence Assessment Tool – Treatment and a clinical interview were used to assess decision-making abilities (understanding, appreciating and reasoning) and judgements of DMC. We limited analysis to patients able to express a choice about treatment and stratified the analysis by low and high understanding ability.

Most people scoring low on understanding were judged to lack DMC and there was no difference by hospital (P=0.14). In both hospitals there were patients who were able to understand yet lacked DMC (39% psychiatric v. 13% medical in-patients, P<0.001). Appreciation was a better ‘test’ of DMC in the psychiatric hospital (where psychotic and severe affective disorders predominated) (P<0.001), whereas reasoning was a better test of DMC in the medical hospital (where cognitive impairment was common) (P=0.02).

Among those with good understanding, the appreciation ability had more salience to DMC for treatment in a psychiatric setting and the reasoning ability had more salience in a medical setting.

Mental capacity is an emerging ethical legal concept in psychiatric settings but its relation to clinical parameters remains uncertain. We sought to investigate the associations of regaining capacity to make treatment decisions following approximately 1 month of in-patient psychiatric treatment.

We followed up 115 consecutive patients admitted to a psychiatric hospital who were judged to lack capacity to make treatment decisions at the point of hospitalization. We were primarily interested in whether the diagnosis of schizophrenia and schizoaffective disorder associated with reduced chances of regaining capacity compared with other diagnoses and whether affective symptoms on admission associated with increased chances of regaining capacity. In addition, we examined how change in insight was associated with regaining capacity in schizophrenia, bipolar affective disorder (BPAD)-mania, and depression.

We found evidence that the category of ‘schizophrenia or schizoaffective disorder’ associated with not regaining capacity at 1 month compared with BPAD-mania [odds ratio (OR) 3.62, 95% confidence intervals (CI) 1.13–11.6] and depression (OR 5.35, 95% CI 1.47–9.55) and that affective symptoms on admission associated with regaining capacity (OR 1.23, 95% CI 1.02–1.48). In addition, using an interaction model, we found some evidence that gain in insight may not be a good indicator of regaining capacity in patients with depression compared with patients with schizophrenia and BPAD-mania.

We suggest that clinico-ethical studies using mental capacity provide a way of assessing the validity of nosological and other clinical concepts in psychiatry.

An individual's right to self-determination in treatment decisions is a central principle of modern medical ethics and law, and is upheld except under conditions of mental incapacity. When doctors, particularly psychiatrists, override the treatment wishes of individuals, they risk conflicting with this principle. Few data are available on the views of people regaining capacity who had their treatment wishes overridden.

To investigate individuals' views on treatment decisions after they had regained capacity.

One hundred and fifteen people who lacked capacity to make treatment decisions were recruited from a sample of consecutively admitted patients to a large psychiatric hospital. After 1 month of treatment we asked the individuals for their views on the surrogate treatment decisions they received.

Eighty-three per cent (95% CI 66–93) of people who regained capacity gave retrospective approval. Approval was no different between those admitted informally or involuntarily using Mental Health Act powers (χ2 = 1.52, P = 0.47). Individuals were more likely to give retrospective approval if they regained capacity (χ2 = 14.2, P = 0.001).

Most people who regain capacity following psychiatric treatment indicate retrospective approval. This is the case even if initial treatment wishes are overridden. These findings moderate concerns both about surrogate decision-making by psychiatrists and advance decision-making by people with mental illness.

In England and Wales mental health services need to take account of the Mental Capacity Act 2005 and the Mental Health Act 1983. The overlap between these two causes dilemmas for clinicians.

To describe the frequency and characteristics of patients who fall into two potentially anomalous groups: those who are not detained but lack mental capacity; and those who are detained but have mental capacity.

Cross-sectional study of 200 patients admitted to psychiatric wards. We assessed mental capacity using a semi-structured interview, the MacArthur Competence Assessment Tool for Treatment (MacCAT–T).

Of the in-patient sample, 24% were informal but lacked capacity: these patients felt more coerced and had greater levels of treatment refusal than informal participants with capacity. People detained under the Mental Health Act with capacity comprised a small group (6%) that was hard to characterise.

Our data suggest that psychiatrists in England and Wales need to take account of the Mental Capacity Act, and in particular best interests judgments and deprivation of liberty safeguards, more explicitly than is perhaps currently the case.

Mental capacity is now a core part of UK mental health law and clinicians will increasingly be expected to assess it. Because it is a legal concept there is a need to clarify associations with variables that clinicians are more familiar with, especially insight.

In this cross-sectional study we recruited consecutive psychiatric admissions to the Maudsley Hospital, London. We carried out structured assessments of decision making using the MacArthur Competence Assessment Tool for Treatment (MacCAT-T), resulting in a clinical judgement about capacity status. We analysed associations with a range of sociodemographic and clinical variables, including insight score on the Expanded Schedule for the Assessment of Insight (SAI-E). The same variables were compared in an analysis stratified according to diagnostic group: psychotic disorders/bipolar affective disorder (BPAD)/non-psychotic disorders.

Psychotic disorders and manic episodes of BPAD are most strongly associated with incapacity. In such patients, insight is the best discriminator of capacity status. In patients with non-psychotic disorders, insight is less strongly associated with capacity; in this group depressed mood discriminates capacity status whereas it does not in psychotic disorders. Cognitive performance does not discriminate capacity status in patients with psychotic disorders.

Mental capacity has complex relationships with psychopathological variables, and these relationships are different according to diagnostic group. Insight is the best discriminator of capacity status in psychotic disorders and BPAD but not in non-psychotic disorders.

Previous work on the reliability of mental capacity assessments in patients with psychiatric illness has been limited.

To describe the interrater reliability of two independent assessments of capacity to consent to treatment, as well as assessments made by a panel of clinicians based on the same interview.

Fifty-five patients were interviewed by two interviewers 1–7 days apart and a binary (yes/no) capacity judgement was made, guided by the MacArthur Competence Assessment Tool for Treatment (MacCAT-T). Four senior clinicians used transcripts of the interviews to judge capacity.

There was excellent agreement between the two interviewers for capacity judgements made at separate interviews (kappa=0.82). A high level of agreement was seen between senior clinicians for capacity judgements of the same interview (mean kappa=0.84)

In combination with a clinical interview, the MacCAT–T can be used to produce highly reliable judgements of capacity.