Children as young as 10 have been driven to attempt suicide or have suffered serious mental health problems after being trafficked as sex slaves or forced laborers in situations "akin to torture", researchers said on Tuesday.

They interviewed 387 boys and girls aged between 10 and 17 in Cambodia, Thailand and Vietnam who had been trafficked for sex work, forced begging and fishing.

Even though global estimates suggest that millions of boys and girls are in forced labor, trafficked or exploited in the sex industry, little is known yet about their health and wellbeing.

Some 56 percent of those surveyed were depressed, a third suffered from an anxiety disorder and around a quarter had post-traumatic stress disorder, according to the study published in the JAMA Pediatrics journal.

Twelve percent of victims said they had tried to harm or kill themselves in the month before the researchers interviewed them, while almost 16 percent reported having suicidal thoughts.

"These findings are especially disturbing given estimates that each year thousands, if not millions of children are trafficked and suffer severe abuse, such as being beaten up, tied or chained, choked, burned, cut with a knife and subjected to sexual violence," said Cathy Zimmerman, one of the authors of the study.

"Children and adolescents who survive trafficking experiences have been through very difficult, often extremely abusive circumstances, sometimes akin to situations of torture," Zimmerman of the London School of Hygiene and Tropical Medicine (LSHTM) told the Thomson Reuters Foundation in an email.

ABUSE AND VIOLENCE

Just over half of those surveyed had been exploited for sex work and 15 girls had been trafficked to China as brides.

One third of the total had been abused sexually or physically, or both, mostly by their trafficker or employer.

Sexual violence was more common among girls, who represented 82 percent of those surveyed.

About a quarter of girls trafficked into sex work experienced physical violence, and 71 percent reported sexual violence by a client.

Even though counseling is available for child sex trafficking survivors, services are insufficient in dealing with victims experiencing such high levels of mental health issues, said Ligia Kiss, a lecturer at the London School of Hygiene and Tropical Medicine, who led the study.

"Staff of post-trafficking services often don't feel equipped to deal with mental health problems, especially with situations involving suicidal intent and alcoholism," Kiss said.

Only the most severe cases and life-threatening mental health conditions ended up receiving appropriate help, she added.

Kiss also noted that a fifth of the children in the study had experienced physical or sexual violence at home before being trafficked, often perpetrated by a family member.