About half the asylum seekers in detention on Manus Island and Nauru are suffering from significant depression, stress or anxiety, according to clinical assessments.
Their situation is worse than for those in detention on the mainland and Christmas Island, where a third are suffering major mental health illness, the assessments show.
In both cases, the number of asylum seekers with serious mental health illness and the severity of the conditions is increasing the longer they are held in detention.
Most of the findings are included in a report by International Health and Medical Services (IHMS), the organisation contracted to provide medical services in detention centres for the Department of Immigration and Border Protection.
They include a spike in reports of asylum seekers on Christmas Island suffering from trauma and torture, “indicating a high level of need for torture and trauma counselling services on the island”.
The findings indicate the number of people in immigration detention who have clinical symptoms of post-traumatic stress disorder is “well over one thousand”.
The findings, obtained by Fairfax Media, will be cited by opponents of mandatory and indefinite detention as the most credible evidence yet that its toll on the mental health of asylum seekers is entirely predictable.
Covering the period from January to March this year, the report reveals that about 13 per cent of those in mainland detention centres and on Christmas Island are suffering from extremely severe depression on arrival.
The percentage grows to 22 per cent for those in detention between four and six months and peaks at 44 per cent for those detained more than 19 months.
The report covers a period when more than 5400 asylum seekers were in detention in mainland centres and on Christmas Island. Almost 70 per cent had been in detention for six months or more.
Although the report highlights the need for “specialist torture and trauma counselling services as well as psychiatrists and clinical psychologists within the detention network”, specialists blame the “detention environment” rather than inadequate services for the worsening mental health of detainees.
Fairfax Media revealed last week that Manus Island has been without a full-time psychiatrist for more than three months.
Dr Peter Young, the medical director for mental health of IHMS, referred to the findings for all centres, including Manus and Nauru, in general terms when he addressed the annual congress of the Australian and New Zealand College of Psychiatrists this month.
Dr Young spoke of the “deterioration in mental health status” for those in detention and “differential effects in different immigration detention environments”. He said IHMS had ”compiled the most complete set of data produced from the detention population”.
Dr Choong-Siew Yong, a former member of the government’s disbanded health advisory group on detention, said it was clear the length of time in detention correlated with more severe symptoms.
“People are coming as asylum seekers with a high level of mental health problems to begin with, and in the environment of the detention centres and the uncertainty around outcomes and the fact they are often in detention for long periods of time, those problems remain and in some cases get worse despite the provision of treatment,” he said.
Dr Yong said he was especially concerned about the mental health of children, who make up 13 per cent of the detention population.