"Trafficking is a crime of global proportions involving extreme forms of exploitation and abuse," write the study authors.
The study on the health of trafficking survivors, published in The Lancet Global Health, was carried out by researchers from the London School of Hygiene & Tropical Medicine in the UK and the International Organization for Migration.
"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," says lead author Dr. Ligia Kiss. "Research is needed to identify effective forms of psychological support that can be easily implemented in low-resource settings and in multilingual, multicultural populations."
According to the researchers, recent estimates suggest that over 18 million people worldwide are forced into labor due to human trafficking. These estimates are difficult to verify, however, due to the hidden nature of trafficking.
"Exploitation of human beings is age-old," state the authors. "Although it is disheartening to see that human trafficking exists in such proportions in the 21st century, it is encouraging that various forms of these violations are increasingly recognized for what they are: modern-day slavery."
For the study, face-to-face interviews were conducted with a total of 1,015 people entering different forms of post-trafficking services in Cambodia, Thailand and Vietnam. The participants were asked questions concerning their living and working conditions, experiences of violence and other health-related outcomes.
In addition to these questions, the researchers also measured for symptoms of anxiety, depression and post-traumatic stress disorder (PTSD), in order to estimate the effect of trafficking on the participants' mental health.
The researchers state that an estimated 56% of forced laborers across the world live in the Asia and Pacific region. In particular, the Greater Mekong subregion - where Cambodia, Thailand and Vietnam are located - is home to over 13 million migrant workers.
Participants reported having been trafficked to work in a variety of different sectors, including sex work (32%), fishing (27%) and factories (13%).
'Support required for physical and psychological health needs of trafficking survivors'
The interviews revealed that many of the participants had experienced terrible working and living conditions, with a significant number describing health problems, both physical and mental.
Almost half (48%) of the participants reported experiencing physical violence, sexual violence or both. Over a third of women and girls (35%) had experienced sexual violence. One fifth (20%) of participants had been locked in a room, and 47% had been threatened at some point.
Perhaps unsurprisingly, 22% of participants with data available (222 of 983) reported sustaining a serious injury at work, including deep cuts, back injury or losing a body part. Despite the severity of these, only 28% of these participants received any medical care for the injuries they sustained.
The mental health burden on the participants was also high. Depression was reported by 61.2% of participants, anxiety by 42.8%, and PTSD by 38.9%. A total of 5.2% admitted to attempting suicide during the previous month.
"Our study shows there is no single profile of a trafficked person," says study author Dr. Cathy Zimmerman. "We spoke to men, women and children of all different ages, from different countries, and with a range of experiences of exploitation."
The study is limited by only including people entering post-trafficking services in the sample, and so the findings may not represent the experiences of the entire trafficked population. However, the authors argue that their large sample collected data from a diverse range of individuals from different settings.
"Finally, the instruments we used to measure mental health outcomes are not diagnostic and should be interpreted only as preliminary indicators for emotional distress and disorder," caution the authors.
Dr. Zimmerman states that the wide range of sectors in which the examples of abuse occur suggests that increased government regulation and stringent health and safety standards are required to improve the situation. Although human trafficking is being acknowledged as modern-day slavery, acknowledgment alone is not enough.
"[Alongside] global condemnation, there needs to be commensurate support for the physical and psychological health needs of survivors of trafficking," argue the authors. "We urge decision makers and donors to invest in post-trafficking health and other services to support the recovery of trafficking survivors."
In November, a report published in The Lancet stated that current global efforts to tackle violence against women - including domestic violence, female genital mutilation and trafficking - are "inadequate."