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.

Secondary parameters are:

• patient barriers and facilitators in the acceptation of nutritional supplements, which will be identified in a short semi-structured interview.

• costs of time spent by staff members on aggression incidents and additional costs of incidents

• patient self-report aggression levels as measured with the Aangepaste Versie van de Agressie Vragenlijst (AVL-AV) (Hornsveld et al., 2009)

• patient observer rated aggression levels as measured with the Socil Dysfunction and Aggression Scale (SDAS) (Wistedt et al., 1990)

• patient observer rated affective symptoms as measured with the Verkorte Comprehensive Psychiatric Rating Scale (vCPRS) (Asberg et al., 1979)

• patient quality of life as measured with the World heath Organization Quality of Life (WHOQL-bref) (De Vries et al., 1995)