An Iranian refugee and her son have been returned to Nauru from Taiwan in a pre-dawn transfer which went against psychiatric advice that the son not be returned because his severe mental illness is caused by his detention.

Fatemah and her 17-year-old son, who Guardian Australia will refer to as Hamid, had been in Taiwan for two months after they were medically transferred from the Australian-run immigration centre.

Fatemah had been waiting 18 months for critical heart surgery but refused to be separated from Hamid, who was suicidal after more than five years on Nauru.

Psychiatric reports said Hamid’s mental illness was caused and exacerbated by his detention, and he should not be returned, but early on Thursday morning officers from the Australian Border Force took him and his mother from their Taipei accommodation and put them on a plane.

[After publication of this article, a Taiwan representative in London said in an email to the Guardian that the ABF had not been involved: According to information provided by the Taiwan Adventist hospital, the two “were peacefully escorted by Australian medical contact personnel, social workers, and staff dispatched by the hospital”. See footnote]

On Tuesday the pair’s caseworker had sought to renew their visas to stay in Taiwan but two days later officials arrived at their accommodation and told them to pack, Fatemah said. Their phones were taken from them and they were taken in two separate vans to a charter jet, with four guards accompanying each of them, she said.

Fatemah said during his last visit with a psychiatrist her son was told ABF was going to transfer the pair to the US, but neither have sat for a resettlement interview and the US government’s travel ban has been blamed for all Iranian and Somali refugees being rejected.

She said they had been accused of lying about conditions in Nauru.

I have been officially accepted as a refugee, but still live in a tent.

Numerous medical reports from 2014 to 2018, seen by the Guardian, have detailed the physical and mental health problems of Fatemah and Hamid.

In a video interview filmed last week, before their removal, Fatemah spoke of her son’s distress.

“My son says to me, ‘let’s attempt suicide together’,” she said. “He believes the only way to freedom is in death. I have sympathy for all the mothers and their children who live in Nauru. We are preyed on and our lives are subjected to cruelty.”

Fatemah and Hamid were sent to Taiwan under a relatively new Australian government policy, which allows critically ill refugees and asylum seekers being detained offshore to receive high-level care in a third country that is not party to the refugee convention.

Both had been seeing a psychiatrist while there, and a recent report from Hamid’s at the Taiwan Adventist hospital found that being held indefinitely on Nauru was contributing to and causing his mental illness.

“The depressive symptoms were not improved, moreover, he had persistent suicide ideation and some organised plans,” the report said.

“I have already prescribed [an] antidepressant for him and told his mother, who is also a patient with major depression, to accompany him. After discussing with the patient, his mother and their case manager, I think the environment in Nauru is [not only] not helpful with his depression, but even the trigger of his depression.”

Australia's refugee deal 'a farce' after US rejects all Iranian and Somali asylum seekers Read more

The Department of Home Affairs in Australia has been contacted for comment. [After the publication of this article, Taiwan’s deputy representative in London wrote a letter to the Guardian setting out Taiwan’s role in the case. The terms of Taiwan’s agreement with Australia to treat some asylum seekers state that “the arrangement is temporary, and the two refugee patients were fully informed of this prior to their arrival in Taiwan and agreed to leave the country once they completed their treatment”. It was wrong to suggest that their departure was opposed by medical personnel, Shyang-yun Cheng wrote.

[In a subsequent email, Shyang-yun Cheng added: “Only Ms Fatemah applied to come to Taiwan for medical treatment. At no point was her son included as a patient in her application. Taiwan, noting her son’s status as a minor, agreed to allow him to accompany her out of humanitarian considerations . . . . The implication that Fatemah and Hamid both entered Taiwan as critically ill refugees is also inaccurate.” See footnote]

Fatemah accused the Australian government of treating her and her son, as well as other refugees, worse than “a criminal in a third world country”.

“I don’t know what to say about the way the Australian government has treated us. I have been officially accepted as a refugee, but still live in a tent,” she said.

Nauru sources and observers have reported a growing crisis of mental illness among the more than 140 refugee and asylum seeker children on the island.

On three separate occasions it has taken urgent court action before the Australian government has agreed to transfer three pre-teenage children suffering acute mental illness to Australia for critical medical care after repeated suicide attempts.

• This article was updated on 18 May 2018 to include post-publication comments sent by Taiwan’s representative office in London, and to link the article to a subsequent letter from that office on this subject.

