the difficulties of predicting future violence edward p. mulvey, ph.d. western psychiatric institute...
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The difficulties of The difficulties of predicting future predicting future
violenceviolence
Edward P. Mulvey, Ph.D.Edward P. Mulvey, Ph.D.Western Psychiatric Institute and Western Psychiatric Institute and
ClinicClinicUniversity of Pittsburgh School of University of Pittsburgh School of
[email protected]@upmc.edu
Conference on Campus ViolenceConference on Campus ViolenceColumbia Law SchoolColumbia Law School
April 4, 2008April 4, 2008
Goals Goals
Provide some background about Provide some background about general methods for making general methods for making predictions of violencepredictions of violence
Identify the inherent challenges to Identify the inherent challenges to predicting campus violencepredicting campus violence
Make some general recommendations Make some general recommendations about strategies for addressing this about strategies for addressing this problemproblem
Actuarial ApproachActuarial Approach
Same information considered for Same information considered for every personevery person
Consistent method for combining Consistent method for combining informationinformation
Factors considered not necessarily Factors considered not necessarily “causal” for that individual“causal” for that individual
Clinical ApproachClinical Approach
Individualized judgmentIndividualized judgment
Range of relevant factors considered Range of relevant factors considered is very broad; ideally, an integrative is very broad; ideally, an integrative viewview
Operates from a theory of how Operates from a theory of how violence might occur or unfold in the violence might occur or unfold in the individual’s lifeindividual’s life
Problems with the Actuarial Problems with the Actuarial ApproachApproach
All the information has to be All the information has to be availableavailable
Generally assumes that all the Generally assumes that all the factors apply the same to everyonefactors apply the same to everyone
The risk estimate is devoid of theoryThe risk estimate is devoid of theory
Problems with the Clinical Problems with the Clinical ApproachApproach
Depends on the person doing itDepends on the person doing it Variability in:Variability in:
Information gatheredInformation gathered Ways information is combinedWays information is combined
Human biases occurHuman biases occur RecencyRecency VividnessVividness
Affected by organizational demands Affected by organizational demands Optimization is assumedOptimization is assumed ““Satisficing” is more commonSatisficing” is more common
Actuarial vs. Clinical Actuarial vs. Clinical PredictionPrediction
Old debate Old debate SuicideSuicide Job/academic successJob/academic success
General findingsGeneral findings Actuarial Approach generally more Actuarial Approach generally more
accurateaccurate Clinical Approach more versatile Clinical Approach more versatile
Issue of reliability and validity Issue of reliability and validity
Actuarial Risk Assessment ToolsActuarial Risk Assessment Tools General violence/recidivism (mainly in mentally ill General violence/recidivism (mainly in mentally ill
individuals)individuals) Historical-Clinical-Risk Management-20 (HCR-20) Historical-Clinical-Risk Management-20 (HCR-20) Violence Risk Appraisal Guide (VRAG) Violence Risk Appraisal Guide (VRAG) Classification of Violence Risk (COVR)Classification of Violence Risk (COVR) Violent Offender Risk Assessment Scale (VORAS)Violent Offender Risk Assessment Scale (VORAS)
Special purpose instrumentsSpecial purpose instruments Domestic violence Domestic violence
Spousal Assault Risk Assessment (SARA)Spousal Assault Risk Assessment (SARA) Risk of sex offenseRisk of sex offense
Static-99 Static-99 Risk of violence among juvenilesRisk of violence among juveniles
Early Assessment Risk List for Boys (EARL-20B) Early Assessment Risk List for Boys (EARL-20B) Manual for the Structured Assessment of Violence Risk in Youth (SAVRY)Manual for the Structured Assessment of Violence Risk in Youth (SAVRY)
Issues regarding actuarial Issues regarding actuarial instrumentsinstruments
Increasingly popular because of technologyIncreasingly popular because of technology Optimization on chanceOptimization on chance
Shrinkage inevitableShrinkage inevitable Application on particular sample might not Application on particular sample might not
be appropriatebe appropriate Effect of contextEffect of context
Information availabilityInformation availability Outcome of decision Outcome of decision
Not a replacement for clinical judgment. Not a replacement for clinical judgment. Integration of actuarial and clinical Integration of actuarial and clinical information is the goalinformation is the goal
Problem #1: Low Base Problem #1: Low Base RatesRates
Actually violent Actually violent
YesYes NoNo
PredictedPredicted Yes 80Yes 80180180 260 260
Violent Violent NoNo 2020 720720 740740
100100 9009001,0001,000
Assume that one in ten individuals is actually violent over a given time period
Assume that the instrument correctly identifies 80% of the violent individuals80% of the nonviolent individuals
true positives
true negativesfalse
negatives
false positives
ImplicationsImplications
No technology will predict rare eventsNo technology will predict rare events Secret Service study of school shootings: Secret Service study of school shootings:
“There is no accurate or useful profile of the “There is no accurate or useful profile of the school shooter”. school shooter”.
““profiles” may be valuable, but not because profiles” may be valuable, but not because they are predictivethey are predictive
The utility of screening and assessment The utility of screening and assessment is not to predict for an individual, but is not to predict for an individual, but to identify groups with higher base ratesto identify groups with higher base rates to focus prevention resources to focus prevention resources
Problem #1: Low Base Problem #1: Low Base RatesRates
Problem #2: Context Problem #2: Context matters and situations matters and situations
changechange
Problem #2: Context Problem #2: Context matters and situations matters and situations
changechange Violence is usually Violence is usually
dependent on proximal situational dependent on proximal situational factors factors
transactional transactional
Opportunities for violence Opportunities for violence may differ substantially across may differ substantially across
individualsindividuals can be altered by lifestyle changescan be altered by lifestyle changes
presence of alcohol presence of alcohol living arrangementsliving arrangements
ImplicationsImplications
Risk statusRisk status may be important, may be important, but so are fluctuations in but so are fluctuations in risk risk statestate Move toward management of high Move toward management of high
risk individuals and situations risk individuals and situations Conditional prediction modelConditional prediction model
““if….then” formulation of riskif….then” formulation of risk Monitoring and management of Monitoring and management of
“dynamic predictors”“dynamic predictors”
Study DesignStudy Design Select group of individuals who were highly likely to Select group of individuals who were highly likely to
have frequent involvement in violencehave frequent involvement in violence
Weekly interviews providing daily reportsWeekly interviews providing daily reports Violent incidents Violent incidents Substance use reports at daily levelSubstance use reports at daily level
Alcohol (number of drinks)Alcohol (number of drinks) Marijuana useMarijuana use Other drugs (mostly cocaine)Other drugs (mostly cocaine)
Analyses of the concurrent and lagged relationships Analyses of the concurrent and lagged relationships of substance use and violenceof substance use and violence
Conditional Probability SERIOUS VIOLENCE
Conditional Probability ANY VIOLENCE
P (violence| alcohol only) 2.3 % 7.9%
P (violence| marijuana only ) 1.6 % 4.2%
P (violence| other drug only) 2.5 % 7.4%
P (violence| alcohol and mj) 4.4 % 10.5%
P (violence| alcohol and otherdrugs) 4.5 % 10.2%
P (violence| alcohol, mj, otherdrugs) 9.0 % 19.4%
P (alcohol | violence) 21.7 % 20.2%
P (marijuana | violence) 32.4 % 28.0%
P (other drugs| violence) 6.2 % 5.5%
P (alcohol & any drug use) 9.3 % 9.3%
P (alcohol & any drug use| violence) 23.1 % 21.0%
SeriouSerious s
violencviolencee
Any Any violenceviolence
Alcohol Alcohol (> 3 (> 3
drinks)drinks)
MarijuaMarijuanana
Other Other drugsdrugs
Percent of Percent of daysdays
1.4%1.4% 3.9%3.9% 8.7%8.7% 20.6%20.6% 2.5%2.5%
Day Before
Day AfterSerious Violenc
eAlcohol
Marijuana
Other Drugs
Serious Violence 5.4 1.9 1.5 2.1
Alcohol 2.4 9.5 2.1 2.8
Marijuana 1.6 2.3 31.5 1.5
Other Drug 1.5 2.2 1.5 48.1
Odds ratios for substance use and Odds ratios for substance use and violence violence
one day apart for serious violenceone day apart for serious violence
ExamplesExamples
--------|||||||-|----------------------------------------------------|---|-----
Case 8
Case 2080
-|------|------------|------|---------------|-|------|--------------|---------|--|--------|----|---|------|------------|------|---------------|-|------|--------------|---------|--|--------|----|--
Testing the relation of Testing the relation of violence and alcohol use over violence and alcohol use over
time time
FindingsFindings Evidence for a lagged effect for alcohol Evidence for a lagged effect for alcohol
use (greater than three drinks) on use (greater than three drinks) on violence, but not the other way aroundviolence, but not the other way around
No significant lagged relationships No significant lagged relationships either way for marijuana use or other either way for marijuana use or other drugsdrugs
Even controlling for different types of Even controlling for different types of substance use, violence on one day substance use, violence on one day predicts for the next daypredicts for the next day
Use of multiple substances on prior day Use of multiple substances on prior day also increases likelihood of violencealso increases likelihood of violence
Problem #1: Low Base Problem #1: Low Base RatesRates
Problem #2: Context Problem #2: Context matters and situations matters and situations
changechange
Problem #3: Late Problem #3: Late adolescence is all about adolescence is all about
change change
Problem #3: Late Problem #3: Late adolescence is all about adolescence is all about
changechange Late adolescence brings: Late adolescence brings:
Independent social roles Independent social roles ““trying on” lifestylestrying on” lifestyles ongoing brain developmentongoing brain development Different patterns of substance useDifferent patterns of substance use
Onset period for many mental disordersOnset period for many mental disorders Substance abuse: 20 years oldSubstance abuse: 20 years old Mood disorders: 30 years oldMood disorders: 30 years old Schizophrenia: 20 years old (males); 30 Schizophrenia: 20 years old (males); 30
years old (females)years old (females) Involvement in violence drops off, even Involvement in violence drops off, even
in serious offendersin serious offenders
Self Reported Offending Self Reported Offending Serious Adolescent Offenders - Serious Adolescent Offenders -
males only – average age 16 at first males only – average age 16 at first interviewinterview
0
2
4
6
8
0 6 12 18 24 30 36
Months after Initial Interview
Se
lf R
ep
ort
Va
rie
ty
Sc
ore Group Group
4 4 (15.1%(15.1%
))
Group Group 5 5
(8.5%)(8.5%)
Group Group 2 2
(33.8%(33.8%))
Group Group 3 3
(18.3%(18.3%))
Group Group 1 1
(24.2%(24.2%))
ImplicationsImplications
Lack of solid history for use in making Lack of solid history for use in making judgments about future violence judgments about future violence
Mix of developmental features and valid Mix of developmental features and valid symptomssymptoms Impulsiveness, moodiness, feelings of being Impulsiveness, moodiness, feelings of being
picked on, feelings of rejection, tendency to picked on, feelings of rejection, tendency to blame othersblame others
Diagnostic labels are less validDiagnostic labels are less valid
Likely to confuse Likely to confuse risk markersrisk markers with with risk risk factorsfactors
Assessments have a limited shelf lifeAssessments have a limited shelf life
1. Get the right 1. Get the right information on the right information on the right individualsindividuals
Screen Screen using structured measures, using structured measures, and and assessassess for risk when warranted for risk when warranted
Use all available information Use all available information consistentlyconsistently
Use relevant assessment toolsUse relevant assessment tools Group characteristicsGroup characteristics Target behavior of interestTarget behavior of interest Use actuarial instrument as an “anchor”Use actuarial instrument as an “anchor”
Best Bets for individual Best Bets for individual assessmentassessment
history of violencehistory of violence impulsivity (process from ideation to action)impulsivity (process from ideation to action) active ideation (mainly hostility and anger)active ideation (mainly hostility and anger) drug and alcohol usedrug and alcohol use psychopathypsychopathy perceived threatperceived threat plan/access to meansplan/access to means opportunities for violent encountersopportunities for violent encounters coping strategiescoping strategies
2. Consider history in detail2. Consider history in detail
When there is past violence, assess:When there is past violence, assess: what happenedwhat happened what factors explain the incidentwhat factors explain the incident what factors protect against violencewhat factors protect against violence which risk and protective factors are which risk and protective factors are
currently in effect or likely to be in effectcurrently in effect or likely to be in effect When there is no past violence, assess:When there is no past violence, assess:
““close calls”close calls” recent changes in life that may exceed recent changes in life that may exceed
coping capacitycoping capacity risk factors for violence, based on risk factors for violence, based on
appropriate assessment protocolsappropriate assessment protocols
3. For prevention efforts, 3. For prevention efforts, distinguish between risk distinguish between risk markersmarkers and risk and risk factorsfactors Key is to focus on causal, dynamic risk Key is to focus on causal, dynamic risk
factorsfactors
QuestionsQuestions Is this a risk factor for a particular type of Is this a risk factor for a particular type of
violence?violence? Are there conditions that influence the Are there conditions that influence the
relationship between the risk factor and relationship between the risk factor and violence?violence?
Does the risk factor play a Does the risk factor play a causalcausal role in role in violence? violence?
If so, is the risk factor capable of being If so, is the risk factor capable of being modifiedmodified??
4. Take context and risk 4. Take context and risk state seriouslystate seriously
A single risk assessment is useless A single risk assessment is useless without a management planwithout a management plan
Assess individual factors and Assess individual factors and conditions periodically in high risk conditions periodically in high risk casescases
Create an environment where students Create an environment where students trust authorities enough to share trust authorities enough to share information information