A new survey from the U.S. Centers for Disease Control and Prevention shows that sexual violence against children is a global problem.

Seven countries were surveyed from 2007 to 2013. The first was Swaziland, which wanted to assess and address the problem. The rate of sexual violence against girls was 36.7 percent. Additional countries asked to be surveyed as well. Young people from the age of 13 to 24 were interviewed, with a range of 1,000 to 2,000 for each gender.

In most countries, more than 1 in 4 girls and more than 1 in 10 boys said they'd experienced sexual violence.

To learn more, we spoke to Dr. Steven Sumner, lead author of the report on the data and a medical epidemiologist at CDC's Division of Violence Prevention.

Who conducted the survey?

There's CDC, there's UNICEF and most importantly there are the in-country agencies. The host country's census or statistical agency trained workers to conduct face-to-face interviews. Males only interviewed males, females only interviewed females. All of the interviews were in a private location where no one can hear the interview.

No parents were involved?

The interviewers were talking to the youth.

Did parents give consent?

When the household is approached a general consent is asked of the parent [for] a survey about the life experiences of the child. Then a second consent is done with the young person in which the survey worker explains the content of the survey and asks if the [young person] would like to complete the survey.

Do many people drop out?

Overall response rates are excellent with a lot of countries hitting the high 80 to 90 percent rate.

The definition of "sexual violence" includes "unwanted sexual touching, unwanted attempted sex, pressured/coerced sex or forced sex." Do some people think "sexual touching" isn't as serious as the other behaviors?

That's a common misperception. But one of the things we're finding from preliminary analyses is that unwanted sexual touching and attempted sex often come before completed sex. They're important not to ignore, sort of warning signs.

I do want to mention [unwanted sexual touching and attempted sex] are harmful to children in and of themselves.

What's the difference between pressured sex and forced sex?

"Pressured" refers to coercion so that could be some form of manipulation whether financial or psychological or other. Forced sex would involve physically forcing the individual.

The perpetrators could be family members but other people as well?

Generally speaking the perpetrators of sexual violence [against children] are known to the victims — a family member or an acquaintance. That's true in many countries. Are there differences between countries? That's something we're looking into.

Since people may be reluctant to talk about abuse, is it possible the actual rates are higher than what the survey shows?

I think you're correct. In general these numbers are probably an underestimate.

What kinds of interventions would help?

CDC's division of violence is promoting a technical package called THRIVES. It's a combination of proven interventions: training in parenting and violence prevention, household economic strengthening, reduced violence through legal protection, improving services, periodic surveillance to see how children are doing.

Why is household economy important?

From other studies, we know economic hardship often is a risk factor for violence.

How do you let young people know help is available?

One of the early things Swaziland did is conduct a large outreach campaign across television stations, radio programs and other communication channels.

The report lists the physical and mental problems children are vulnerable to after abuse: depression, unwanted pregnancy, sexually transmitted diseases. I was surprised to see diabetes and cardiovascular disease cited. How does sexual violence lead to those conditions?

It's something scientists call toxic stress: extreme trauma that can lead to hormonal or biochemical changes in a child's developing body that can affect their growing organs, which includes their brain and other systems.

The rates of violence in the survey were about 1 in 4 for females, 1 in 10 for men. How does that compare to the United States?

In the United States measures of sexual violence against children are recorded in the National Survey of Children's Exposure to Violence. In the most recent version when they asked 14-to-17-year-olds in the U.S., about 1 in 5 females and about 1 in 20 males said they had experienced some form of sexual assault, from touching to forced sex.

Did anything surprise you about the survey?

To me, the most striking finding was how few children were getting help.

The report notes: "In most countries surveyed, the proportion of victims that received services, including health and child protective services" was 10 percent or lower.

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