An al-Jazeera journalist captured in Afghanistan six years ago and sent to Guantanamo Bay is close to becoming the fifth detainee at the US naval base to take his own life, according to a medical report written by a team of British and American psychiatrists

Sami al-Haj, a Sudanese national, is 250 days into a hunger strike which he began in protest over his detention without charge or trial in January 2002. But British and American doctors, who have been given exclusive access to his interview notes, say there is very strong evidence that he has given up his fight for life, experiencing what doctors recognise as "passive suicide", a condition suffered by female victims of Darfur.

Dr Dan Creson, a US psychiatrist who has worked with the United Nations in Darfur, said Mr Haj was suffering from severe depression and may be deteriorating to the point of imminent death.

He said the detainee's condition was similar to that of Darfuri women in Sudan whose mind suddenly experiences an irreversible decline after enduring months of starvation and abuse. He said: "In the midst of rape, slow starvation, and abject humiliation, they did whatever they could to survive and save their children; then, suddenly, something happened in their psyche, and, without warning, they would just sit down with their small children beneath the first small area of available shade and with no apparent emotion wait for death."

In June this year a Saudi man became the fourth prisoner to take his own life at Guantanamo Bay. Guards found him dead in his cell. Two Saudis and a Yemeni prisoner were found hanged in an apparent suicide at Guantanamo in June last year. A senior US officer caused outrage at the time by describing the suicides of three men as an act of asymmetric warfare and a good PR move on the part of terrorist suspects.

Mr Haj, 38, was sent on assignment by al-Jazeera television station to cover the war in Afghanistan in October 2001. The following month, after the fall of Kabul, Mr Haj left Afghanistan for Pakistan with the rest of his crew.

In early December, the crew were given visas to return to Afghanistan. But when Mr Haj tried to re-enter Afghanistan with his colleagues, he was arrested by the Pakistani authorities – apparently at the request of the US military.

He was imprisoned, handed over to the US authorities in January 2002, taken to the US military compound in Bagram, Afghanisatan, then Kandahar, and finally to Guantanamo in June 2002.

His lawyer, Clive Stafford Smith, of the human rights charity Reprieve, said his client had endured months of brutal force-feeding and lost nearly a fifth of his body weight during the hunger strike.

Mr Stafford Smith said: "The US military is rightly afraid of a fifth prisoner dying in their custody. But they wrongly respond by treating prisoners worse. Blankets and clothes are removed in case they are used to commit suicide. The harshest methods of forced feeding are deployed – Sami has suffered the feeding tube being forced down into his lungs by mistake several times."

The warning about the condition of Mr Haj coincided with the release of Guantanamo transcripts which describe the hostility between guards and their prisoners. The transcripts includes details of guards interrupting detainees at prayer, detainees flinging body waste at guards and interrogators withholding medicine.

Dr Hugh Rickards, a British psychiatrist, warned in his report that the level of Mr Haj's mental suffering "appears so acute that it is my duty as a medical practitioner to put this in writing to ensure appropriate assessment and treatment".

Dr Mamoun Mobayed, a British psychiatrist based in Northern Ireland, and a third member of the team who has also been given access to written notes of recent interviews with the prisoner, said there was also concern about the mental health of Mr Haj's wife and seven-year-old son, who was just one when his father went on assignment to Afghanistan.