"Enola Holmes" star Millie Bobby Brown, who is now 16, was cyberbullied while appearing in "Stranger Things." She was only 12 when she started the role, and by 14 she had to shut down her Twitter account to escape the abuse.

Recently she wrote: "... the inaccuracy, inappropriate comments, sexualization, and unnecessary insults ... ultimately have resulted in pain and insecurity for me. But not ever will I be defeated."

Good for her. But tweens aren't always able to find the strength to deal with cyberbullying. According to Tween Cyberbullying 2020, a new report from Cartoon Network and the Cyberbullying Research Center, online abuse is a growing problem for younger kids now that 21% of 9-year-olds and 68% of 12-year-olds have an Internet-enabled smartphone.

The report found that 15% of tweens have witnessed cyberbullying; 6% have been cyberbullied many times; and 8.5% report being cyberbullied once or twice.

Among kids who've been targets, nearly 70% say it negatively impacted their self-esteem. Almost one-third said it affected their friendships, 13.1% said it affected their physical health, and 6.5% said it impacted their schoolwork.

The report urges parents to open up a dialogue with their tweens about the issue, and if they find their child is affected, to give unequivocal support, find out what your child wants to do about it, and offer suggestions for stopping it from happening.

Visit these websites with your tween for information on how to proceed: stopbullying.gov; National Bullying Prevention Center at pacer.org/bullying; and the Cyberbullying Research Center at cyberbullying.org.