Victims of human trafficking in Britain suffer from severe mental health problems as a result of the abuse they experienced and need adequate support from health services to help them recover, experts said on Thursday.

Nearly 80 percent of women and 40 percent of men who have been trafficked in Britain reported high levels of depression, anxiety and symptoms of post traumatic stress disorder (PTSD), they wrote in a study in the American Journal of Public Health.

"Even after escaping trafficking, the large majority of people in our sample reported that they were still afraid of their traffickers," Si'n Oram, lead author of the study from the Institute of Psychiatry, Psychology and Neuroscience (IoPPN) at King's College London, said in a statement.

"It is crucial ... that the immediate safety of survivors is taken into consideration when planning the type of support required."

The researchers interviewed 150 people trafficked to Britain from 30 countries, including Nigeria, Albania and Poland, for what the experts said was the first study of the impact of trafficking on mental health in a high-income country.

Women were trafficked to Britain mainly for sexual exploitation or domestic servitude while the majority of men were trafficked for labor exploitation in farming, construction and car washing, the study said.

It said 66 percent of trafficked women reported being sexually exploited, including more than half the women trafficked for domestic servitude.

Healthcare, including physical, mental and sexual care, must be a fundamental part of support for the survivors of trafficking, the researchers said.

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"(Human trafficking) damages the physical and psychological health of men and women exploited in many different labor sectors," said Cathy Zimmerman, co-investigator from the London School of Hygiene and Tropical Medicine.

"The NHS (National Health Service) has a key role to play in helping trafficked people to recover from their ordeal, and in the UK response to human trafficking."

Last year Britain passed the Modern Slavery Act to crack down on traffickers and bring in measures to protect people feared to be at risk of being enslaved.

The Home Office (interior ministry) estimates that up to 13,000 people are victims of slavery in Britain, forced to work in factories and farms, sold for sex in brothels or kept in servitude behind closed doors.