A retrospective survey of contemporaneous electronic case records in a male psychiatric intensive care unit (PICU) in central London was carried out for 2012. The notes were scrutinised for records of serious violence where there was threat to life or limb that resulted in patients being given rapid tranquillisation and seclusion. The survey revealed that of 72 admitted individuals, 58% were responsible for this degree of behaviour. Most incidents (67%) were perpetrated in multiples by slightly fewer than 25% of all those who were admitted. This suggests an average of 3 serious incidents per patient.

In a meta-analysis on in-patient aggression, ^{Reference Dack, Ross, Papadopulous, Stewart and Bowers1} a literature review shows that the estimated percentage of aggression on acute admission wards is extremely variable, with figures quoted from 8 to 44%. A third of in-patients have experienced violent or threatening behaviour, with higher figures for staff - 41% of clinical staff and almost 80% of nursing staff working in in-patient units have experienced aggressive behaviour. It is important therefore to understand the strength of association between risk factors for in-patient aggression and the extent to which these disruptive and distressing events can be predicted and prevented.

In the present retrospective survey, it was clear from the data that the incidence of violence decreased consistently week on week; 45% of all behaviours (n=80) requiring emergency nursing intervention occurred in the first week of all admissions. This reduced to 15% by the second week and 7.5% by the third week, however, by week 8 there was a rise to 13%. This is an interesting observation which may indicate the point at which PICU becomes counter-productive. Department of Health guidelines for PICU admission recommend that admission should not ordinarily exceed 8 weeks. ²

The observation that the first week represents the highest risk period of an admission fits in well with previous data. This high-risk period could be an opportunity to monitor imminent behaviours through routine enhanced nursing observations, allowing a proactive rather than reactive response style bearing the brunt of staff/patient interactions. ^{Reference Papadopolous, Ross, Stewart, Dack, James and Bowers3,Reference Bowers, Gournay and Duffy4} The observations of week-on-week reduction in serious violence could be explored further with a case-control study. Although resource intensive, ultimately any procedure that is likely to reduce violence to staff and patients is worth pursuing.