What we know and don’t know about how mass trauma affects mental health
Researchers are trying to figure out who is most at risk of self-harm
![a group of students at a memorial in Parkland, Fla.](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2019/04/032919_SG_trauma_feat.jpg?fit=860%2C460&ssl=1)
ONE YEAR LATER Thousands gather in Parkland, Fla., to remember the 17 students killed in a mass shooting a year earlier at Marjory Stoneman Douglas High School. Two recent suicides highlight the lingering trauma from the event.
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