Depression is common in people with dementia, and negatively affects quality of life.

This paper aims to evaluate the cost-effectiveness of an intervention for depression in mild and moderate dementia caused by Alzheimer's disease over 12 months (PATHFINDER trial), from both the health and social care and societal perspectives.

A total of 336 participants were randomised to receive the adapted PATH intervention in addition to treatment as usual (TAU) (n = 168) or TAU alone (n = 168). Health and social care resource use were collected with the Client Service Receipt Inventory and health-related quality-of-life data with the EQ-5D-5L instrument at baseline and 3-, 6- and 12-month follow-up points. Principal analysis comprised quality-adjusted life-years (QALYs) calculated from the participant responses to the EQ-5D-5L instrument.

The mean cost of the adapted PATH intervention was estimated at £1141 per PATHFINDER participant. From a health and social care perspective, the mean difference in costs between the adapted PATH and control arm at 12 months was −£74 (95% CI −£1942 to £1793), and from the societal perspective was −£671 (95% CI −£9144 to £7801). The mean difference in QALYs was 0.027 (95% CI −0.004 to 0.059). At £20 000 per QALY gained threshold, there were 74 and 68% probabilities of adapted PATH being cost-effective from the health and social care and societal perspective, respectively.

The addition of the adapted PATH intervention to TAU for people with dementia and depression generated cost savings alongside a higher quality of life compared with TAU alone; however, the improvements in costs and QALYs were not statistically significant.

UK Biobank is a well-characterised cohort of over 500 000 participants including genetics, environmental data and imaging. An online mental health questionnaire was designed for UK Biobank participants to expand its potential.

Describe the development, implementation and results of this questionnaire.

An expert working group designed the questionnaire, using established measures where possible, and consulting a patient group. Operational criteria were agreed for defining likely disorder and risk states, including lifetime depression, mania/hypomania, generalised anxiety disorder, unusual experiences and self-harm, and current post-traumatic stress and hazardous/harmful alcohol use.

A total of 157 366 completed online questionnaires were available by August 2017. Participants were aged 45–82 (53% were ≥65 years) and 57% women. Comparison of self-reported diagnosed mental disorder with a contemporary study shows a similar prevalence, despite respondents being of higher average socioeconomic status. Lifetime depression was a common finding, with 24% (37 434) of participants meeting criteria and current hazardous/harmful alcohol use criteria were met by 21% (32 602), whereas other criteria were met by less than 8% of the participants. There was extensive comorbidity among the syndromes. Mental disorders were associated with a high neuroticism score, adverse life events and long-term illness; addiction and bipolar affective disorder in particular were associated with measures of deprivation.

The UK Biobank questionnaire represents a very large mental health survey in itself, and the results presented here show high face validity, although caution is needed because of selection bias. Built into UK Biobank, these data intersect with other health data to offer unparalleled potential for crosscutting biomedical research involving mental health.

UK Biobank is a well-characterised cohort of over 500 000 participants that offers unique opportunities to investigate multiple diseases and risk factors.

An online mental health questionnaire completed by UK Biobank participants was expected to expand the potential for research into mental disorders.

An expert working group designed the questionnaire, using established measures where possible, and consulting with a patient group regarding acceptability. Case definitions were defined using operational criteria for lifetime depression, mania, anxiety disorder, psychotic-like experiences and self-harm, as well as current post-traumatic stress and alcohol use disorders.

157 366 completed online questionnaires were available by August 2017. Comparison of self-reported diagnosed mental disorder with a contemporary study shows a similar prevalence, despite respondents being of higher average socioeconomic status than the general population across a range of indicators. Thirty-five per cent (55 750) of participants had at least one defined syndrome, of which lifetime depression was the most common at 24% (37 434). There was extensive comorbidity among the syndromes. Mental disorders were associated with high neuroticism score, adverse life events and long-term illness; addiction and bipolar affective disorder in particular were associated with measures of deprivation.

The questionnaire represents a very large mental health survey in itself, and the results presented here show high face validity, although caution is needed owing to selection bias. Built into UK Biobank, these data intersect with other health data to offer unparalleled potential for crosscutting biomedical research involving mental health.

G.B. received grants from the National Institute for Health Research during the study; and support from Illumina Ltd. and the European Commission outside the submitted work. B.C. received grants from the Scottish Executive Chief Scientist Office and from The Dr Mortimer and Theresa Sackler Foundation during the study. C.S. received grants from the Medical Research Council and Wellcome Trust during the study, and is the Chief Scientist for UK Biobank. M.H. received grants from the Innovative Medicines Initiative via the RADAR-CNS programme and personal fees as an expert witness outside the submitted work.