Introduction

Mental health crisis care

People living with challenges to their mental health can experience an acute mental health crisis while living in the community. This can include intense feelings of depression, anxiety or paranoia, including feeling suicidal, and can result in the individual and/or their family and loved ones feeling that they are unable to cope without urgent, professional support. In England, people who are already using secondary mental health services in the NHS might be able to contact their care coordinator, an out-of-hours service or mental health crisis line, and be referred directly to crisis care services. For example, they might receive regular visits from a crisis resolution and home treatment (CRHT) team for a short period until the immediate crisis has passed or be admitted to psychiatric inpatient care for a period of assessment and/or treatment. People who are not already in contact with mental health services, or who are unable to wait to be referred to specialist care, will often present at hospital emergency departments (ED). People who self-harm or attempt suicide as a result of their distress can self-present at, or be transported to, an ED by emergency services. In ED, people will first be triaged by a member of the ED team and if a mental health need is identified – and once any immediate medical need (e.g. resulting from self-injury) is resolved – be seen by a member of the liaison psychiatry, assessed, and follow-up care arranged (including, if deemed necessary, a psychiatric inpatient admission).

Mental health crisis care, as described above, is under intense pressure in the UK1 and in equivalent systems internationally.2–6 Visits to EDs for mental health issues are increasing while the number of available psychiatric inpatient beds is decreasing, resulting in challenges to the ED system7 and lengthy waits in ED for people in mental health crisis.8 In England, the ED system has been described as near breaking point.9 Approximately two in three of all people with multiple attendances at ED have been in contact with specialist mental health services or have had a previous acute psychiatric admission,10 with frequent attenders at greater risk of psychiatric inpatient admissions.11 People presenting with a mental health issue are over six times more likely than people presenting with a physical concern to wait more than 4 hours at the ED12 (in England breaches of a 4-hour wait are a key performance indicator for EDs). Mental disorders are estimated to account for around 5% of ED attendances in the UK and almost 30% of acute inpatient bed occupancy and acute readmissions.13 Poor experiences and low levels of satisfaction with mental health care all point to the ED as not being a far from ideal environment for support and treatment for mental health crisis.12,14

Psychiatric inpatient stays can be costly,15 in some cases detrimental to mental health,16 disproportionately harmful to people from some minority ethnic groups,17 and reportedly unnecessary for as many as 17% of referred individuals.18 Admissions following an acute crisis can be brief (often < 5 days), yet the effectiveness, cost-effectiveness and outcomes of short stays on psychiatric wards followed by early discharge is unclear.19 Bed occupancy in inpatient psychiatric facilities is well above recommended levels with 91% of wards operating above the recommended occupancy rate.13

The emergence of liaison psychiatry services has enabled mental health NHS trusts to provide responsive mental health assessment, advice and onward referral within emergency care settings, but wide variations in service provision20 remain and there are ongoing challenges to sustainability.21 The introduction of CRHT teams22,23 and triage wards24 has offered little benefit in reducing contact with acute services, inpatient admissions or costs across the wider inpatient system compared with standard models of care, with ongoing staff concerns over the accuracy of triage decisions for mental health presentations in ED.25,26 To address these growing challenges, policy in England has called for the development and evaluation of new, more effective models of crisis care as collaborations between health, mental health, social care, third sector and emergency service providers locally.27,28 Alongside new street triage services,29 crisis houses30 and crisis cafes,31 some delivered in the third sector,32 psychiatric decision units (PDUs) have emerged as just one of a number of responses.

The psychiatric decision unit

Psychiatric decision units – also known in England as mental health decision units, crisis assessment units or assessment suites, among similar terms – have been set up in response to policy and the need to manage demand, to reduce unhelpful admissions to acute inpatient care, especially avoidable short admissions and expensive out-of-area or private admissions, and reduce mental health presentations at ED. International counterparts to the PDU fulfil a similar function,33 can be known as a psychiatric emergency service (PES), crisis stabilisation units or behavioural assessment units, and have become increasingly critical to the delivery of mental health crisis care.34–36 This is particularly true for the USA where a third of hospitals are estimated to provide these emergency units,37 but they are also present in, for example, France,38 Singapore39 and Australia.40

There is no single service specification for PDUs in England but rather a shared set of characteristics. PDU are short-stay facilities, based either on psychiatric or general hospital sites, for people in acute mental health crisis, offering time-limited care (typically up to 24–72 hours) including overnight stay. Units target people who experience repeat, often extended stays in ED, frequent use of other services such as the police and ambulance services, and have complex and frequent crisis-related needs but who might not benefit from a psychiatric inpatient stay. The focus of the units is on providing a comprehensive assessment in a calm, safe environment, offering therapeutic input as appropriate, and onward signposting and referral to a range of community-based care, both within and outside the NHS, hopefully breaking the cycle of repeat ED presentation and/or unhelpful acute admission. PDUs are distinguishable from triage or assessment wards; short-stay wards which typically accept all patients likely to require assessment or treatment in an inpatient setting.41 Additionally, PDUs typically only accept informal patients (i.e. people not admitted assessment or treatment sections of the Mental Health Act), whereas triage wards will admit people formally under the Mental Health Act. Furthermore, as admission to PDU is not a formal inpatient admission, PDU staff are not required to complete inpatient treatment plans or the clustering tool for admission as they would on a ward, freeing up more time for individual face to face contact. Staff-to-patient ratio – at around 1 : 2 – is also typically higher than in an inpatient ward (typically around 1 : 4).42 PDUs are often nurse led, supported by healthcare assistants (HCAs), with consulting input from psychiatry and other mental health professionals. PDUs can be co-located and share staffing with a Section 136 Place of Safety. Overnight accommodation is single sex, sometimes with flexible partitioning to enable the unit to respond to different numbers of male and female visitors, generally comprising reclining seating rather than beds. Units tend to be small with a capacity of around six to eight.

Efforts have been made to establish PDUs as an integrated part of the crisis care pathway.43 PDUs accept referrals directly from liaison psychiatry teams based in ED, other mental health crisis services (e.g. CRHT and street triage teams), and sometimes community mental health services, primary care or third sector services – but do not generally accept self-referrals – with formal gatekeeping procedures in place. An example of the location of a PDU in the crisis care pathway in one of our sites can be seen in Figure 1, with the PDU playing a gatekeeping (assessment and referral) role for people identified by crisis services as having a higher level of need than might be met by intensive home treatment yet not in need of a Mental Health Act assessment, and from where a decision can be made about either subsequent inpatient admission or a return home with an appropriate support plan.

FIGURE 1 Crisis care pathway map. (Figure not reproduced here; see the original article.)

Aims and objectives

Although formal evaluations of recently developed PDUs in the USA and Australia have suggested that PDU-type units might reduce length of stay (LOS) in EDs and inpatient psychiatric admissions among people experiencing mental health crisis,37,40 evidence regarding the characteristics and effectiveness of PDUs in England is restricted to informal local evaluations.44,45 While these reports suggest PDUs have potential to reduce demand on ED and psychiatric admissions, key data have not been reported (e.g. LOS in the ED) and study designs have not adequately accounted for variables that might confound comparison. In addition, PDUs in England have been developed organically, in response to policy and the pressure on services rather than the evidence base. There is a need for a clear description of the PDU model, including identification of key variables in unit configuration and function, and an understanding of how PDUs fit alongside other services in the crisis care pathway. It is possible PDUs introduce further fragmentation to the system, and, if not effective, may waste critical resources. As such, a formal evaluation of these services is urgently required to describe the model of care and generate much-needed knowledge about impacts, quality, and cost benefits.

The aim of the study is to ascertain the structure and activities of operational PDUs in England and to provide an evidence base for their effectiveness, costs and benefits, and optimal configuration. The study aim is addressed through the following research questions:

1. What is the range of hospital-based, short stay interventions internationally designed to reduce admissions to acute psychiatric inpatient care and what is their effectiveness?
2. What is the scope and prevalence of PDUs nationally and how are they configured?
3. How has the introduction of PDUs impacted on psychiatric inpatient admissions and ED psychiatric episodes/breaches?
4. What are the care pathways before and following an admission to the PDU?
5. What is the impact of the introduction of PDUs on inequalities of access to acute mental health services?
6. How do service users experience PDUs, as well as crisis care pathways before and after admission to PDU?
7. How are decisions made about referral and admission to PDU, and assessment and onward signposting and referral?
8. How do the economic costs and impacts of PDUs compare with areas without PDUs?
9. How do the costs for individual service users post PDU implementation compare with their costs prior to the introduction of PDUs to crisis care pathways?