Frequently Asked Questions


What is this study about?

Black Americans are 5 times as likely as White Americans to be killed by police while unarmed. These events may be traumatic not just for the direct victims and their families, but also for other people not directly affected. We set out to understand whether police killings of unarmed Black Americans affect the mental health of other black Americans in the general U.S. population.


What did we do?

We linked data on police killings from the Mapping Police Violence database with nationally-representative survey data from the Behavioral Risk Factor Surveillance System, 2013-2015, a telephone survey conducted by all 50 states under the auspices of Centers for Disease Control (CDC). The sample included over 100,000 black Americans.

Our analysis compared the mental health of black Americans interviewed before and after police killings occurring in their state of residence. The primary outcome was the number of days in the past 30 for which a respondent reported poor mental health. Because the specific timing of police killings was random relative to the interview dates, the correlations we observed can be interpreted as the causal effect of police killings on population mental health.


What did we find?

Police killings of unarmed black Americans were associated with a statistically significant increase in mental health morbidity in the wake of those events among other black Americans in the general U.S. population. Each police killing led to a per capita increase of 0.14 poor mental health days per month in the three months after the event (95%CI 0.07 to 0.22 days).

We found that effects were specific to black Americans. We found no effect of police killings of blacks or whites on the mental health of whites, and no effect of killings of armed black Americans.


Are the effects clinically significant?

With black Americans exposed to an average of four police killings per year in the same state, our results suggest that police killings of unarmed blacks contribute to 55 million poor mental health days each year among black Americans nationally. These estimates suggest that the population mental health impact of police killings of unarmed blacks is nearly as large as the mental health burden associated with Type II diabetes – a disease that affects 1 in 5 black adults and is responsible for 75 million poor mental health days per year.


Are the findings credible?

Because the timing of police killings is largely random relative to the interview dates, it is unlikely that our results are due to confounding factors. Supporting a causal explanation, we found no association between police killings and the mental health of respondents interviewed in the period before those police killings occurred. Our results were also specific to the mental health responses of black Americans to police killings of unarmed black Americans. No effect was observed on the mental health of whites, and no effects were observed following police killings of whites or of armed blacks.


How do you interpret the results?

Our findings suggest that events widely perceived to reflect structural racism can have significant mental health impacts on black Americans not directly affected. Police killings of unarmed black Americans – and the paucity of criminal prosecutions of involved officers – have been widely interpreted as a manifestation of structural racism, and as a reflection of the low value placed by society on black lives. These killings are significant given the long history of state-sanctioned violence used to subjugate and terrorize black Americans. Further research will be needed to understand precisely what mechanisms give rise to these adverse mental health effects, including fear of victimization, vicarious experience of trauma, and loss of status. However, given the ubiquity of such secondary exposures to racism in the lives of black Americans, our study suggests that racism may be a significant source of mental morbidity among black Americans.


What was known about this before?

There is a large literature linking directly experienced racism to poor mental health, but less data on indirect exposures to racism. Our findings are consistent with prior evidence of elevated depressive symptoms in communities following the deaths of Freddie Gray and Michael Brown, as well as following high profile events reflecting systemic racism such as the beating of Rodney King. The data we present contribute a national, population-representative perspective and have a causal interpretation.


What are the implications of the study?

  • Police killings of unarmed black Americans have significant effects on the mental health of other black Americans in the general population.
  • Interventions are needed to reduce the prevalence of these killings and to support the mental health of communities affected when they do occur.


If these events are leading to poor mental health, should the media stop covering them and should people stop sharing them on social media?

Our study does not identify whether news reporting, social media, or other channels were responsible for transmitting the observed impacts on mental health. Our study simply shows that more police killings of unarmed black Americans lead to worse mental health for other black Americans. While it is conceivable that media coverage mediates the observed effects, it is also possible that media coverage, sharing on social media, and public protest could be supportive of mental health by validating people’s experiences of these tragedies, and providing forums for people to process their emotions. One of the difficulties in determining the role of traditional or social media in the mental health effects of police killings is that media coverage and social media attention may themselves be a consequence of the mental health response. Further research is needed to understand the role of media and social media.


How did you determine who was exposed to the police killings in their state?

All BRFSS respondents were considered exposed if they were interviewed within three months after a police killing of an unarmed black person in the same state. Thus, we are capturing many different types of exposure, including word of mouth, media, and social media. We are also counting as “exposed” state residents who may not have even known about the police shooting. Whereas our results are valid estimates of population impact, they average over many different experiences and likely underestimate the mental health impacts in some sub-populations.


Please send additional questions to: atheenv@pennmedicine.upenn.edu.