An Australian doctor has been brought to tears by the abuse and trauma he witnessed in Nauru's immigration detention centre.

Paediatrician Dr David Isaacs is one of several doctors, workers and guards turned whistleblowers exposing what they say is a culture of cover up, rape, self harm and abuse on Nauru, in defiance of laws that could land them in prison.

"I saw a six-year-old girl who tried to hang herself with a fence tie and had marks around her neck. I've never seen a child self-harm of that age before," Dr Isaacs told ABC's 7.30.

"After five days, I went home and had nightmares. I didn't expect that.