An actuarial model of violence risk assessment for persons with mental disorders.
OBJECTIVE
An actuarial model was developed in the MacArthur Violence Risk Assessment Study to predict violence in the community among patients who have recently been discharged from psychiatric facilities. This model, called the multiple iterative classification tree (ICT) model, showed considerable accuracy in predicting violence in the construction sample. The purpose of the study reported here was to determine the validity of the multiple ICT model in distinguishing between patients with high and low risk of violence in the community when applied to a new sample of individuals.


METHODS
Software incorporating the multiple ICT model was administered with independent samples of acutely hospitalized civil patients. Patients who were classified as having a high or a low risk of violence were followed in the community for 20 weeks after discharge. Violence included any battery with physical injury, use of a weapon, threats made with a weapon in hand, and sexual assault.


RESULTS
Expected rates of violence in the low- and high-risk groups were 1 percent and 64 percent, respectively. Observed rates of violence in the low- and high-risk groups were 9 percent and 35 percent, respectively, when a strict definition of violence was used, and 9 percent and 49 percent, respectively, when a slightly more inclusive definition of violence was used. These findings may reflect the "shrinkage" expected in moving from construction to validation samples.


CONCLUSIONS
The multiple ICT model may be helpful to clinicians who are faced with making decisions about discharge planning for acutely hospitalized civil patients.
Monahan
John
J
the University of Virginia School of Law, Charlotteville, 22903, USA. jmonahan@virginia.edu
Steadman
Henry J
HJ
Robbins
Pamela Clark
PC
Appelbaum
Paul
P
Banks
Steven
S
Grisso
Thomas
T
Heilbrun
Kirk
K
Mulvey
Edward P
EP
Roth
Loren
L
Silver
Eric
E
D000206:Actuarial Analysis; D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D003710:Demography; D001330:Electronic Data Processing; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology* / Q000534:rehabilitation; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012984:Software; D011795:Surveys and Questionnaires; D014754:Violence / Q000706:statistics & numerical data*