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DENVER (KDVR) — Recalling Sept. 11, 2001, brings haunting images to mind of planes flying into the Twin Towers and people falling to their deaths. Those images and memories continue to impact our collective mental health.

Many may not even realize it.

At Ground Zero, the memorial and museum stirs up strong emotions. Through the painful history, a story is told of the strength and unity experienced after the attacks.

Apryl Alexander, associate professor of forensic psychology at the University of Denver, has analyzed the collective trauma we experienced that day and ever since. She focuses on ways to move forward in a healthy way.

“Seeing those repeated images can trigger things like post-traumatic stress, anxiety, depression,” Alexander said.

On the 20th anniversary — with expanded news coverage and newly released documentaries— more people are reliving that day and suffering through it all over again.

“What we need to be thinking about is how do we protect ourselves when we’re wanting to know the news but also don’t want to be traumatized at the same time,” Alexander explained.

Sometimes protecting ourselves means tuning out a bit.

“If you feel yourself getting physiologically aroused, distressed or disturbed, maybe it’s time to hit the pause button and come back to it later,” Alexander said.

Checking in with your body, as experts say, is important to seeking necessary help and preventing additional trauma. The professor said one of the most common ways people have turned negative emotions into a force for good is through giving back.

“A lot of people got civically engaged [after 9/11],” she said. “You hear those stories of people who became firefighters or nurses or even joined the military after 9/11. Donations even went up after 9/11. Community came together even through this incident of collective trauma … and kind of transformed it into collective resilience.”

To this day — from coast to coast— 9/11 is known as an American day for volunteering and community.

If the upcoming anniversary is something you’re struggling with, the national Disaster Distress Helpline is available 24/7. Call or text 1-800-985-5990 to connect with a trained counselor.