The largest ever health study of trafficking victims has uncovered the brutal scale of modern slavery in Southeast Asia. More than 1,000 survivors from Cambodia, Thailand, and Vietnam delineated the physical and psychological toll their exploitation had wreaked, including sexual abuse, dog attacks, burning, and choking.

Researchers from the London School of Hygiene and Tropical Medicine and the International Organization for Migration interviewed 1,015 people seeking post-trafficking treatment in the three countries, most of whom had been coerced into either sex work (32 percent of those surveyed) or sectors such as fishing and factories.

Defined by the State Department as “when someone obtains or holds a person in compelled service,” modern slavery can take several forms such as forced labor, sex trafficking, child soldiers, and involuntary domestic servitude.

Nearly half of the study’s participants reported physical or sexual abuse (or both), while almost two-thirds said they were suffering from symptoms of depression. Over 40 percent had experienced anxiety, with an additional 38.9 percent diagnosed as having post-traumatic stress disorder.

Of the physical abuse survivors had undergone, many had experienced “extreme violence”—such as knife or dog attacks, or being strangled. More than one-third of women and girls had been sexually assaulted, while 47 percent of all participants had been threatened, and 20 percent had been locked in a room by their employers.

Victims had mostly worked for numerous hours at a time (70 percent of those surveyed said they worked seven days a week) in horrendous conditions, which resulted in 22 percent of participants sustaining a serious injury in the workplace. Less than a third were given medical treatment in the aftermath of such events.

Dr. Ligia Kiss, a lecturer of social epidemiology and the lead author of the study, said: “Our findings highlight that survivors of trafficking urgently need access to health care to address a range of needs, and that mental health care should be an essential component of this. Research is needed to identify effective forms of psychological support that can be easily implemented in low-resource settings and in multilingual, multicultural populations.”

The results come just one day after reports of Thailand’s failure to address its human trafficking problem, with their efforts being branded “wholly inadequate” by the Environmental Justice Foundation, a rights group. “Nothing that we have seen or heard in the last year indicates that Thailand has taken meaningful action to address the root causes of trafficking and abuse,” the organization’s executive director, Steve Trent, said in a statement. The country is now in “tier 3” on the State Department’s list of worst offenders as a result of its abysmal human rights record—the same ranking afforded to North Korea and Iran.

Fishing is one of the country’s most notorious industries for trafficking, with a number of the victims surveyed working 19 hours a day every day of the week, and spending more than a year at sea at a time. One of the study’s participants told researchers he had been at sea for around 10 years, with no means of escape, while others reported having seen injured fishermen being pushed overboard. “Murders were definitely witnessed,” researcher Cathy Zimmerman told the Thomson Reuters Foundation.

One of the study’s key findings concerned the mental health of trafficked women, who were worst affected when forced into either labor or marriage, as opposed to sex work. The most brutal violence was suffered by women trafficked as brides. “Trafficking is not just about sex work, but is about exploitation in a huge range of sectors from which a lot of us probably benefit," Zimmerman added.

John Kerry wrote that there is “perhaps no greater assault on basic freedom than the evil of human trafficking” in 2014’s Trafficking in Persons Report, but there is still an international struggle to crack down on coercion into slavery, which is also prevalent in Central American countries such as Mexico and Guatemala. Though awareness has been raised, few solutions have been reached as to how to put an end to such abuses for good.

“What this study does, is hopefully put numbers to the problem so that real action is taken to prevent exploitation,” said Zimmerman.