Diet and aggression

The main parameter in this study is the number of aggressive incidents in each arm, registered with the Staff Observation Aggression Scale- Revised Version (SOAS-R) (Nijman et al., 1999). As incidents may differ in severity and consequences, we make a distinction between minor (verbal aggression, threats, non-compliance with hospital rules, aggression towards objects, disinhibited [sexual] behaviour) and major (severe threats, fighting, assault on patients or staff, self-harm, suicide attempt) incidents. We carried out a pilot study to determine the prevalence of aggressive incidents among long-term psychiatric inpatients. This study yielded an estimate of 112 incidents per patient per year: 65 verbal aggression incidents, 12 incidents in which aggression was aimed at objects, 8 self-harm incidents, and 27 incidents in which physical aggression was aimed at others. We also monitored the time spent by nursing staff on each of these four types of incidents; verbal aggression took 80 minutes, aggression towards objects cost 77 minutes, self-harm cost 222 minutes, and physical aggression towards others cost 335 minutes per incidents. Based on these results, major incidents will be weighted by a factor 3.8.