The psychiatric intensive care unit (PICU) has been defined as a service that provides care for ‘patients compulsorily detained usually in secure conditions, who are in an acutely disturbed phase of a serious mental disorder. There is an associated loss of capacity for self control, with a corresponding increase in risk, which does not enable safe, therapeutic management and treatment in a general open acute ward’ (Department of Health, 2002). PICUs allow immediate response to critical situations (both within the PICU and in liaison with interface services) and PICU staff have become well versed in responding to emergency conditions within psychiatry.

PICUs evolved pragmatically within general adult psychiatry to provide safe, therapeutic care for patients displaying particularly disturbed or sustained high-risk behaviour that necessitates some security in their treatment. Because they developed unsystematically, at first the care provided seemed haphazard, with much disparity in clinical practice, governance and unit protocols (Zigmond, 1995; Beer et al, 1997; Pereira et al, 1999). In 2002, England's National Association of Psychiatric Intensive Care Units (NAPICU), in conjunction with the Department of Health, developed national standards for PICUs (Department of Health, 2002). Since these standards were published, funding was allocated to upgrade PICU physical environments (Pereira et al, 2005a), a national governance network established (Dye et al, 2005), and an accreditation scheme measuring units against set criteria developed (Cresswell et al, 2009). Since then, national standards have been updated (NAPICU, 2014). This has given managers, clinical staff, patients and relatives a benchmark upon which to base further improvements.

The concept of psychiatric intensive care has expanded to settings other than general adult psychiatry. Similar units have developed within forensic psychiatry, women's services and adolescent services. In the future there might be further developments: perhaps PICUs for older adults, patients with intellectual disabilities and those with personality disorder. Whatever the variant of PICU, all units have a similar ethos of providing intensive, comprehensive, multidisciplinary care for mentally unwell patients whose presentation in an acute phase of illness poses increased risks to themselves or others. Figure 8.1 displays the central positioning of the PICU within the adult mental health service framework.