Table 1.

Studies of the Relationships Between Exposure to a Victim or Perpetrator of Violence in One's Social Network and Individual Risk of Violent Victimization or Perpetration

First Author, Year (Reference No.)	Type of Violence Transmission	Sample			Age	Network Violence Exposure	Violent Outcome	Data Collection Methods	Analytical Methods	Key Findings
		No.	Location	Population
Murphy, 2011 (13)	Violent perpetration by parents → weapon victimization	2,898	United States	Young adults who completed all 3 waves of the National Longitudinal Study of Adolescent Health (Add Health) and who had been in a heterosexual romantic relationship for at least 3 months at the time of the wave III interview	Range, 18–26 years	Parents or other adult caregiver(s) slapped, hit, or kicked the respondent before sixth grade	Victim of weapon violence in the past 12 months (someone shot, cut or stabbed, pulled a knife or gun on, or jumped the respondent)	Participants self-reported the exposure and outcome during the wave III in-home interviews	Logistic regression model adjusted for ethnicity; sex; age; educational attainment; history of sexual abuse and neglect (left home alone, needs not met) before grade 6; and prior victimization (reported at waves I and II)	Physical violence perpetration by parents in childhood was associated with increased odds of weapon victimization in young adulthood (adjusted OR = 1.51) (P < 0.001)
Tucker, 2014 (14)	Violent perpetration by parents → weapon victimization	1,726	United States	Children with at least 1 sibling under age 18 years, from nationally representative sample interviewed in the National Survey of Children's Exposure to Violence	Range, 2–9 years	Witnessed violence perpetrated by parent against other parent, sibling, or another adult in the household in the past year	Victim of severe physical assault (involving a weapon or causing injury) by a sibling in the past year	Adult caregivers reported the exposure and outcome for 1 randomly selected child in the household during telephone interviews	Logistic regression model adjusted for child's race/ethnicity, age, and sex; parent or partner's highest education level; parent's marital status; parent warmth; parent inconsistency/hostility; parent supervision; and interparental conflict	9% of children in the sample had been exposed to parent perpetration of violence; 3% had been severely victimized by a sibling. Witnessing parent perpetration of violence was associated with increased odds of severe victimization by a sibling (adjusted OR = 3.22, 95% CI: 1.53, 6.75) compared with no sibling victimization
Murrell, 2005 (15)	Weapon perpetration by parents → weapon perpetration	362	United States	Male batterers who were court ordered to receive assessment at a domestic violence assessment center, and who had nonmissing data on threatened or actual weapon use	Range, 18–65 years	Witnessed threatened or actual use of a gun or knife by either parent before the age of 16 years	Threatened or actual use of a gun or knife against an intimate partner	Men self-reported the exposure and outcome on written questionnaires. Reports of weapon use by the men against their partners in domestic violence incidents were verified from court records	${\chi }^2$ analysis unadjusted for other covariates	7% of the sample reported witnessing a parent threaten to use or actually use a weapon against an intimate partner; 57% reported threatening or actually using a weapon against an intimate partner themselves. A greater proportion of men who had witnessed parental weapon use during childhood reported threatened or actual weapon use against an intimate partner (83% vs. 55% of men without a witnessing history, P < 0.01)
Khan, 2008 (12)	Violent perpetration by parents → weapon perpetration	111	Scotland	Youth offenders who had been or were currently under the care of the Scottish youth criminal justice or welfare system	Range, 10–19 years (mean = 14.83 years)	Witnessed violence perpetrated by parent(s)	Perpetration of severe violence against a sibling with threats of or actual weapon use	Youth self-reported the exposure and outcome during interviews	Regression model unadjusted for other covariates	36.9% of participants had witnessed or were aware of weapons being used during interparental assaults; 30.6% of participants reported having ever threatened a sibling with a knife, 19.8% wounded a sibling with a knife, 19.8% threatened a sibling with a gun, and 9.9% fired a gun at a sibling
										Witnessing parent perpetration of violence was associated with severe violence with a weapon perpetrated against a sibling (β = 0.24, t = 2.34, P = 0.022)
Casiano, 2009 (16)	Violent perpetration by family member → gun and other weapon perpetration	5,692	United States	Adults representative of the noninstitutionalized civilian population, from the National Comorbidity Survey-Replication	Range, ≥18 years	Witnessed serious physical fights at home, such as father beating up mother, at age 16 or younger	Ever threatened someone with a gun or with another type of weapon, such as a knife, stick, broken bottle, or mace	Participants self-reported the exposure and outcome during interviews	Logistic regression model adjusted for sex, age, race, education, marital status, employment status, income, urbanicity, lifetime mental disorders, childhood physical abuse, and childhood sexual abuse. Separate models were fit for each outcome (threats with a gun and threats with another weapon)	13.1% of the sample reported witnessing domestic violence during childhood; 3.5% and 6.3% reported ever threatening someone with a gun or with another weapon, respectively. Witnessing domestic violence during childhood was associated with having threatened others with a gun (adjusted OR = 2.62, 95% CI: 1.8, 3.8) and with having threatened others with another weapon (adjusted OR = 1.34, 95% CI: 1.0, 1.8)
Vaughan, 1996 (17)	Gun victimization of family or friends → weapon perpetration	2,005	New York, New York	Boys and girls in 3 junior high schools	Range, 11–15 years (students in 7th and 8th grades; mean = 12.8 years)	Close friend or family member was victim of a shooting	Used a weapon on someone	Youth self-reported the exposure and outcome on written questionnaires	Logistic regression model unadjusted for other covariates	41.5% of students reported that a close friend or family member had been shot; 24.0% and 14.0% of boys and girls, respectively, reported having ever used a weapon on someone. Reporting that a close friend or family member had been shot was associated with reporting having used a weapon on someone (OR = 2.8, 95% CI: 2.1, 3.6)
Roberts, 1996 (29)	Weapon perpetration by intimate partner → homicide perpetration	105 homicide perpetrators and 105 abused controls	New Jersey	Abused women who killed their partner or former partner and were in prison and abused control women selected from suburban police departments and battered women's shelters	Not available	Weapon used by intimate partner in worst incident of domestic violence	Killed intimate partner	Women reported the exposure during in-person structured and open-ended interviews	Proportions unadjusted for other covariates	A greater proportion of women who killed their intimate partner reported weapon use by the partner (39.7% vs. 18.8% of abused women in the control sample)
Campbell, 2003 (30)	Gun and other weapon perpetration by intimate partner → homicide victimization	220 femicide cases and 343 abused controls	11 cities in the United States	Femicide cases and control women who had been physically assaulted or threatened with a weapon by a current or former intimate partner during the past 2 years	Range, 18–50 years	Intimate partner had ever threatened the victim with a weapon and/or had used a gun in the most severe incident of abuse	Homicide by intimate partner	For femicide cases, proxy informants who were knowledgeable about the victim's relationship with the perpetrator reported on weapon threats and gun use during in-person or telephone interviews. Control women self-reported the exposure and outcome during telephone interviews	Logistic regression model adjusted for intimate partner employment status, partner and victim access to a gun, whether perpetrator and victim ever lived together, whether victim had a child by a previous partner in the home, partner's level of control over victim, whether partner had previously threatened to kill victim, whether partner had previously forced sex with victim, whether partner had previously been arrested for domestic violence, and characteristics of the most severe abuse incident (victim or perpetrators had used alcohol or drugs, and incident was triggered by victim leaving the perpetrator for another relationship)	55.3% of femicide cases vs. 4.7% of abused controls had been threatened with a weapon by their intimate partner; a gun was used in 38.2% and 0.9% of the most severe abuse incidents for femicide cases and abused controls, respectively. Intimate partner's previous threats with a weapon and use of a gun were associated with femicide (vs. control) status in adjusted models (adjusted OR for threats = 4.41, 95% CI: 1.76, 11.06; adjusted OR for use of gun = 41.38; P < 0.01)
Kingsnorth, 2006 (32)	Weapon perpetration by intimate partner → victimization	872	Sacramento County, California	Heterosexual couples with an intimate partner violence arrest that was closed by the district attorney's office between January 1, 2000, and April 30, 2000, filed as a misdemeanor or violation of probation, and for which information on critical variables was available	Not available	Weapon used in the index abuse incident	Rearrest for an intimate partner violence offense during the 18-month follow-up period after the index incident	Data on the exposure and outcome were obtained from law enforcement arrest and crime reports, California Department of Justice arrest histories, and prosecutor files, including victim services reports	Logistic regression model adjusted for suspect characteristics (any prior arrest, race/ethnicity, employment status, sex, age, substance use, marital status, cohabitation status, protective order in place) and incident characteristics (victim wanted arrest)	A weapon was used in 16.3% of the index abuse incidents; 15.3% of suspects were rearrested for intimate partner physical violence within 18 months of the index incident. Weapon use during the index incident was associated with increased odds of physical violence recidivism (adjusted OR = 2.14, P < 0.05)
Glass, 2008 (31)	Gun perpetration by intimate partner → victimization	84	United States	Women who reported current or past-year physical or sexual violence by a same-sex partner or former partner and who completed a 1-month follow-up interview	Mean = 36.59 (SD, 12.17) years	Intimate partner had ever threatened or used a gun against the victim	Reassault (physical or sexual) or threat of reassault in the past month by the partner or former partner	Women self-reported the exposure during baseline telephone interviews and the outcome during 1-month follow-up telephone interviews	Relative risk ratios unadjusted for other covariates	Threat or actual use of a gun by an intimate partner was reported by 14.7% of the sample; one third of the sample reported threatened or actual reassault at follow-up Intimate partner's previous threatened or actual use of a gun was associated with an increased risk for reassault (RRR = 1.93, 95% CI: 0.79, 4.75)
Folkes, 2013 (11)	Weapon perpetration by intimate partner → victimization	1,421	Ontario, Canada	Male offenders who had committed a physical assault or made a death threat against a wife or cohabiting female partner	Mean = 37.1 (SD, 11.1) years)	Intimate partner used or threatened to use a firearm or used a weapon in the index abuse incident	No. of occurrences of physical assault against a female partner that were recorded in police reports or criminal records after the index incident, and measures of severity of recidivism	Data on the exposure and outcome were obtained from occurrence reports filed by police in Ontario, Canada, as well as criminal records maintained by the Canadian Police Information Center.	Correlation analysis unadjusted for other covariates	3 men (0.2%) used a firearm in the index assault, whereas 21 men (1.5%) threatened to use a firearm. 88 men (6.2%) used a weapon (including a firearm) in the index assault. 32% of the men violently recidivated against a female partner after the index assault (with a mean follow-up of 5.4 years, SD, 1.43)
										The offender's weapon use in the index assault was not associated with physical assault recidivism (r = 0.05) or with measures of the severity of domestic violence recidivism (r = −0.03 to 0.02)
Bonomi, 2014 (33)	Weapon perpetration by intimate partner → victimization	5,994	Seattle, Washington	Couples who had a male-to-female perpetrated intimate partner violence incident reported to the Seattle Police Department during 1999–2001, with nonmissing census tract information for the location of the incident	Range, ≥18 years	Weapon involvement (guns, rifles, knives, or vehicles) in the index abuse incident	No. of police-reported physical abuse incidents during the 2-year period after the index incident, where physical abuse included assault, homicide, rape, reckless endangerment, and unlawful imprisonment	Data on the exposure and outcome were obtained from the Seattle Police Department's Domestic Violence Unit database, which includes information recorded by police officers responding to reported incidents.	Generalized estimating equation Poisson regression models were used to account for individuals nested within census tracts. Models were adjusted for characteristics of the index abuse event, including victim and perpetrator race/ethnicity and age; perpetrator drug and alcohol use; victim pregnancy; type of abuse (physical or nonphysical); victim injury; police arrest; and quartiles of neighborhood per capita income based on the census tract of the incident location	5.2% of the index abuse events included weapon involvement; 13% of women experienced physical intimate partner violence during the 2-year follow-up period. Weapon perpetration by a male intimate partner at the index abuse event was associated with 72% more physical abuse incidents during the follow-up period (adjusted IRR = 1.72, 95% CI: 1.29, 2.30)
Haynie, 2006 (46)	Violent perpetration by peers → weapon perpetration	12,747	United States	Adolescents who completed the in-school survey and first 2 in-home interview waves of the National Longitudinal Study of Adolescent Health (Add Health), who provided an address, and who had parents who completed the parent questionnaire and friends who completed the in-school survey	Mean = 15.8 years	Peer involvement in physical fights in the past 12 months	Serious violent behaviors in the past 12 months (pulled a knife or gun on someone, shot or stabbed someone, used a weapon in a fight, hurt someone badly enough to need medical care)	Participants were asked to identify up to 5 of their closest friends of each sex from a school roster; the friends' own responses from in-school surveys about physical fighting were averaged to create the exposure measure of peer violence. Serious violent behaviors were self-reported by the participants in the wave II in-home interviews	Hierarchical linear models were used to account for individuals nested within neighborhoods. Models were adjusted for neighborhood characteristics (disadvantage, residential instability, immigrant concentration, population size); peer school orientation; age and age squared; sex; race; family structure; family socioeconomic status; parent-child relationship quality; mother's age; parent reasons for selecting neighborhood; no friends identified by respondent; and respondent's own school orientation and fighting (from wave I).	11% of the sample reported serious violent behaviors in the past 12 months. Peer fighting was associated with serious violent behavior (β = 0.18 for a 1- SD increase in peer fighting; SD, 0.03)
Papachristos, 2012 (8)	Gun victimization of peers → gun victimization	763	Boston, Massachusetts	Individuals, including reported gang members and their associates, in the Cape Verdean community	Mean = 24.87 (SD, 6.33) years	Mean social distance between individual and gunshot victims in social network; percentage of immediate associates who were gunshot victims	Fatal or nonfatal gun victimization	Field intelligence observations from the Boston Police Department in 2008 were used to identify ties between individuals who were observed in each other's presence by police. A list of immediate associates of all Cape Verdean gang members known to the police was first created; another list of “friends” was then created from field intelligence observations on these associates. Records on all fatal and nonfatal gunshot injuries reported to the police in 2008–2009 were used to identify the outcome	Rare event logistic regression models adjusted for individual characteristics (sex, ethnicity, age squared, history of arrest) and network variables (ego-network density and percent of immediate associates who were gang members)	The average shortest distance to a gunshot victim was 4.69 ties (SD, 2.91), and the average percent of an individual's immediate associates who were gunshot victims was 8% (SD, 21%). 5% of the sample were victims of gun violence. The farther one is from a gunshot victim in one's social network, the lower one's own odds of gun victimization (adjusted OR = 0.91, 95% CI: 0.84, 0.99 for each social tie removed from a victim); having a greater percentage of immediate associates who were gunshot victims was associated with increased odds of gun victimization (adjusted OR = 2.44, 95% CI: 1.11, 5.36 for an increase of 1 percentage point)
Papachristos, 2014 (47)	Gun homicide victimization of co-offenders → gun homicide victimization	8,222	Chicago, Illinois	Individuals who were arrested between 2006 and 2011 in a high-crime community and who had co-offending ties to at least 1 other person	Mean = 27.4 (SD, 9.68) years	Mean social distance between individual and gun homicide victims in the co-offending network	Gun homicide victimization between 2006 and 2011	Arrest records from the Chicago Police Department were used to identify known co-offenders (i.e., ≥2 people arrested together for the same crime) and create co-offending networks. Homicide records from the Chicago Police Department were used to identify the outcome	Logistic regression models adjusted for individual characteristics (age, age squared, African-American race, sex, gang membership) and network characteristics (network degree (total no. of ties), ego density (proportion of individual's associates who were also tied to each other), whether an individual was a member of the largest network component, and geographical distance to the nearest homicide victim)	On average, any individual in the network was 5.4 ties away from a homicide victim; the average shortest path to a homicide victim of all possible paths was 10.53 ties (SD, 2.59). The farther one is from a gun homicide victim in the co-offending network, the lower one's own odds of gun homicide (adjusted OR = 0.42, 95% CI: 0.27, 0.65, for each social tie removed from a victim)
Papachristos, 2015 (48)	Nonfatal gun victimization of co-offenders → nonfatal gun victimization	169,725	Chicago, Illinois	Individuals who were arrested between January 1, 2006, and September 30, 2012, and who had co-offending ties to at least 1 other person	Mean = 25.7 years	Percentage of one's associates who are nonfatal gunshot victims	Nonfatal gunshot injury	Arrest records from the Chicago Police Department were used to identify known co-offenders and create co-offending networks. Data on nonfatal gunshot injuries from the Chicago Police Department were used to identify the outcome	Logistic regression models adjusted for individual characteristics (sex, age, gang member, race) and network characteristics (network degree and membership in the largest network component).	The average percentage of immediate associates who were victims of gunshot injuries was 6.3% (SD, 16.7%). Having higher percentages of one's associates who were nonfatal gunshot victims was associated with higher odds of nonfatal gunshot injury (e.g., OR = 3.13, SD, 0.06, for an increase in 1 percentage point of immediate associates who are gunshot victims).

Abbreviations: CI, confidence interval; IRR, incidence rate ratio; OR, odds ratio; RRR, relative risk ratio; SD, standard deviation.