“#IfIDieInPoliceCustody Know that the color of my skin was the only crime committed,” a woman tweeted in 2015, three days after Sandra Bland was found dead in her Texas jail cell.

“Nothing will happen to the Police in the Freddie Gray case . . . ” a man tweeted three days after the death of a 25-year-old Baltimore man whose fatal spinal injury while in police custody in 2015 triggered protests throughout the nation.

These sentiments — perception of a systemic unfairness and a loss of faith in institutions — are common among black people in the days and months following police killings of unarmed African Americans, according to a study published last month in the medical journal the Lancet.

The report analyzed data collected between 2013 and 2016 from 103,710 black adults, finding the incidents to be detrimental to the psyche, adding 1.7 days of poor mental health annually per person. The study also analyzed white Americans’ self-reported mentality after all police killings (of  white and black people), determining that “mental health impacts were not observed.”

Atheendar Venkataramani, a co-author of the study, told The Washington Post that these findings did not mean white people had no emotional reaction to killings. But their responses, he said, haven’t “crossed the line from being upsetting to something that can create or cause disease.”

The paper said the decline in black mental health was seen in all black Americans, regardless of whether there was a relationship with the victim, and can manifest itself in a variety of ways, including “reactions of anger, activation of prior traumas and communal bereavement.”

“Structural racism experienced vicariously can be very consequential for [black] mental health,” said Venkataramani, who is a professor at the University of Pennsylvania’s Perelman School of Medicine. “We are not telling people in the black American community something they do not already know.”

University of Texas at Austin professor Christen Smith told The Post in an email that society has “treated police violence like an acute crisis that only impacts those violated and/or killed and to some extent their immediate kin.”

“This study pushes us to think more broadly about the impact of police violence however,” she wrote. “Police violence poses a mental health threat to the black community writ large, which means that our social responsibility is much greater than we previously thought.”

In the study, researchers cross-referenced results of a government health survey with police killings that occurred in the same state as respondents. Incidents came from Mapping Police Violence, a database that tracks police killings in all 50 states and the District of Columbia. The killings included ranged from shootings to people who died of health issues while in police custody.

Of the nearly 1,000 people who were killed by police in 2017, 223 were black, according to a database maintained by The Post. A Post analysis found that African American males in 2017 were “shot at disproportionately high rates,” accounting for 22 percent of all victims while making up only 6 percent of the U.S. population.

Researchers noted they were “underpowered to examine mental health effects of police killings among other vulnerable populations, such as Hispanics and Native Americans,” but think work on the subject should be done.

Smith, who studies black women and racial formation, said “the consequences of this [study] are clear — we must undo the policies that allow for the continuation of police killings and acknowledge and treat racial trauma as a mental-health issue that impacts our broader society.”

Steven Rich and Scott Clement contributed to this report. 

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