The screaming started about 4.30am on March 28 in Lima Dorm, the single women's quarters at Villawood Immigration Detention Centre. Wang Meihui, a Chinese detainee who had lost her claim for asylum as a Falun Gong follower, was dragged from her bed by four security guards. Barefoot, still in her pyjamas, she was carried to a van, driven to the airport and deported to China. There had been no warning from authorities she was to be taken.

As terrified faces appeared at bedroom doors, guards held tight to the doorknobs of her friends' rooms so they could not come out and help her.

"I have never heard such a horrible noise, like an animal struggling for their life," says 24-year-old Lee Jiao, who says her door was held shut. "After that, life in Villawood changed. The 6am Falun Gong exercises stopped. Three women went on a hunger strike."

The following day, a spokesman for the Immigration Minister told the ABC the woman had not been removed with force.

One of those hunger strikers was Zhao Mei, a 50-something Falun Gong detainee. For 51 days she refused to take food, dropping 13 kilograms to 37 kilograms. "Because the woman they deported was Falun Gong, we went on the hunger strike to support her," Zhao says.

Immigration officials finally convinced Zhao to end her fast by promising to personally review her claims and send an official from Canberra. Three months after the hunger strike (she has now spent more than a year at Villawood), she remains in detention limbo. She has been moved from Lima Dorm to a low-security shared house, but remains terrified that the guards will come for her.

On this day, she sits huddled over a table in the carport, weeping constantly and too weak to walk properly. "I am living a frightened life every day, especially after what happened on March 28. I never forget, not even now, here. I hear it every night."

Mandatory detention for unauthorised arrivals was introduced in 1992 and applies to asylum seekers arriving by boat or air and anyone else without a valid visa.

Initially there was a 273-day limit on detention but this was removed by the then Labor government in 1994. The High Court confirmed that year that authorities had the power to hold "unlawful non-citizens" indefinitely. By the mid-1990s, the medical community had begun to sound warnings about the impact of mandatory detention on detainees.

The number of asylum seekers peaked in 1999-2000, with 4174 people, mainly Iraqis, Iranians and Afghans who had fled persecution, locked up in remote jail-like centres on arrival in Australia. Today that number has fallen to 483. There are 89 asylum seekers held on Nauru under the Government's controversial "Pacific solution". The Howard Government says mandatory detention is an important part of its border-security strategy to deter unauthorised arrivals.

The revelation of how Cornelia Rau, an Australian resident, was treated in South Australia's Baxter detention centre put the spotlight on Australia's inhumane treatment of detainees and led to significant changes in the way they are held and the length of time, asylum seekers, at least, are detained.

Rau is still seeking compensation for her ordeal through the courts. Because women have made up a small proportion of the detainee population, their needs in detention and, once out, in the wider community have received little attention.

Of detainees in Australia, 53 are women (27 in detention centres and 26 in community or residential detention). Villawood, in Sydney's south-west, houses by far the largest group of women, 21.

Zachary Steel, a senior lecturer in psychiatry at the University of NSW, and his colleague Professor Derrick Silove have been monitoring the effect of detention on asylum seekers for more than 10 years. Mental health professionals are only now beginning to assess the long-term effect of detention. "People are fairly resilient, but those who spent more than six months in detention, that was the threshold, then they crumbled and three years later they were still disturbed, with no major improvement," Steel says.

"Comparing people who came to Australia through the non-detention route to those who went through detention, three years after release, the people detained were still experiencing post-traumatic stress disorder on a daily basis where the intrusions were about detention, not about what

they went through in their home country." Steel, Silove and Patricia Austin will this month publish a comprehensive review of the impact of detention on the mental health of detained asylum seekers in the journal Transcultural Psychiatry.

Steel says post-traumatic stress continued to affect people once they were released on three-year temporary protection visas. Interviews with former asylum seekers found the stress of detention and the visas were equal to anything they had encountered up to that point.

Temporary visas were introduced by the Howard Government in 1999, with a view to repatriating visa holders if the situation in their countries of origin improved.

"Even though we were technically meeting our protection obligations it shows that for a person's psychiatric integrity, they need to know they are safe," Steel says. "You can't live a normal life knowing you may be sent back to a place where you have been tortured.

"The very existence of TPVs will rewrite the whole understanding of post-traumatic stress disorder in the world."

The disorder received a lot of attention after the Vietnam War, when troops left a dangerous place and returned to safety. "We had started to think of this syndrome as past-oriented. But what we saw among TPVs was that their nightmares are all future-directed."

Because temporary visas do not allow for family reunions, they created a phenomenon of women and children seeking unauthorised arrival. "Men used to escape first, find a safe haven and then try to bring out their families," Steel says. "They couldn't do that, so you had the waves of women and children. That is why the SIEV-X was filled with them [353 people died when the boat sank in 2001]. We wouldn't have had that. It was an inadvertent consequence of this policy."

In a series of interviews with the Herald, women in detention, or who spent time there and are now out, opened up about their fears, the toll detention takes on their families and marriages, and their inability to trust a Government that would lock them away. The names of some have been changed because those in detention fear persecution if they are forcibly returned to their countries of origin, and many of those now living in the community fear the Australian Government might take revenge on them by changing the laws and sending them home.

Women have always been the minority in immigration detention. "Safety is always a real issue for women; my experience and that of my colleagues was that the system was universally unable to protect women," Steel says. "I heard horrendous tales of women being left alone in single men's compounds, unbelievable negligence."

With overcrowding no longer an issue in detention centres, the threat to the women in them has lessened.

Djamileh Vambakhsh (her real name) was not a refugee but she stayed at Villawood for several weeks when she emigrated, via Japan, from Iran more than 20 years ago.

"There was no razor wire, even for refugees; it was a nice, normal place. Five years ago, I went back, I saw the razor wire, I saw the kids. I was sick," she says. Since then she has helped Iranian women survive inside and adjust when they enter the community.

For two years she has run a creative writing class for Farsi speakers, initially just for women, through the Hornsby TAFE. "This allows women to tell their stories as fiction, as if it happened to someone else," she says. "You never tell your stories to anyone because you don't know who you can trust."

Farideh Naseri, an Iranian claiming political persecution, flew to Australia in October 1999 with her children, a son, 7, and daughter, 2, on a false Iranian passport. In her first immigration interview, the 42-year-old says, she was told she would get a temporary visa the next week. Two months later, immigration officials told her she was lying about her political problem. All the time she thought, "I am not somebody who should be in jail. I am not a bad person. Adults understand, but children can't.

"In Villawood, there were fences everywhere, but four times a day you had to go and sign your name. If you didn't go, someone came and pushed hard on the door. Every night, someone came and checked two or three times a night with a light."

Five months after she arrived she received a temporary protection visa. "My daughter was only three years old and she said to me: 'I am happy to be released.' She says her son, now 15, cannot forget his time in detention. "He sees a specialist for relaxation, he takes tablets, and always he dreams not good dreams. For five years after the family's release in Sydney, her son insisted on visiting others in Villawood, getting his mother to prepare Persian food to take to the detainees.

For Naseri, the outside in some ways only felt like a bigger detention centre because her husband could not join her while she was on a temporary visa. Only in 2005, after she was granted a permanent protection visa, could he join her from Iran. "For five years I did not see my husband; after the long separation we were not thinking the same way. He is thinking the same as before but I am not the same as before," she says.

"In Iran you live only for children and for study. Here it's not the same."

She says that despite her son's trauma he is working hard and wants to study genetics. Naseri has become a citizen.

For years, detention centres were dominated by Iranians, Iraqis and Afghans but now there is a clear Asian flavour. The majority in detention now come from China and other parts of Asia.

Hui Rong Mesrinejad, 26, says she fled China because of its discriminatory one-child policy. She was the fourth child and "my mother was running and hiding to have me".

When officials heard Hui Rong was living with her boyfriend in 2003, they ordered her to have a contraceptive device fitted, she says. A family member who was forced to have one implanted had suffered serious complications. Rather than face the prospect, Hui Rong left the country in early 2004.

Refugee advocates say that during Chinese New Year in 2005, family planning officials trashed her parents' home as punishment - they had already left the village because of continuing harassment.

Arriving in Australia, via Macau, on a false Portuguese passport, Hui Rong was sent straight to Villawood, where she spent two years and eight months until last October. She met her husband, Amir Mesrinejad, an Iranian asylum seeker, there. When they married on July 1 last year, an immigration official let her out for the day, escorted by guards in casual dress, reportedly saying, "No one should have to get married in that place."

Now she is out, she sits in her lounge room in a quiet street in Guildford, with the curtains closely drawn. Beyond the curtains is a big grassy backyard she does not like to use.

"I don't need to open them, I only need to see inside," says Mesrinejad, whose married name is real (her Chinese name is assumed to protect her family's identity).

The Immigration Department never accepted her one-child policy discrimination claim but she was eventually granted a humanitarian visa. Her husband had previously gained a humanitarian visa after five years in detention.

Both converted to Christianity inside Villawood and Amir Mesrinejad hopes to train for the Anglican ministry at Moore College from next year.

Despite her new freedom, Mesrinejad's world is small. She goes to English classes every day, to Bible study and to church in Carlingford on Sundays. She is frightened to stay alone in the house. The couple are expecting their first baby in January.

Lee Jiao is a bright young Chinese student. The gay 24-year-old Falun Gong follower came to Australia as a 17-year-old, studied English and did two years of civil engineering at the University of NSW, before changing to hospitality and graduating in commercial cooking.

But she did something stupid. She used false identity papers to open a bank account for a "friend".

Lee says the friend threatened to tell her family in China about her homosexuality if she did not help him. But she was to be paid for the job. She got caught, the friend disappeared, and she was given a six-month good behaviour bond. When she applied to renew her visa she was rejected on character grounds because of her criminal record.

She has applied for a protection visa on identity grounds, that she is homosexual and follows Falun Gong. Lee says many detainees do not want to talk about their grounds for appeal but she believes the centre has at least 30 people with Falun Gong claims.

The Chinese Government banned Falun Gong in 1999, describing it as an evil cult that threatened social stability and spread superstitious thinking.

"If you are gay or Falun Gong in China you don't get a job," Lee says. "In my opinion, Australia is very fair: you do the work, you get paid the money. In China, you have relations or you don't get work."

Standing nearby, Ying Hua, 33, stares vacantly across the visitors area. Three years in detention have taken their toll. "I am very depressed, for a long time on medication every night," she says. "I feel very weak and sick, no one else has been here as long. No one from my life before comes to visit.

"Many times I have special care from the officers, watching me, outside my door, checking every few minutes, but it's not real care."

Ying says she left China because she had a political problem with the Chinese Government. She came to Australia in 1998 on a false Thai passport, via Bangkok, but says she did not know where she was going. "Life is terrible for me. I cannot do anything."

Her case has been rejected by the Refugee Review Tribunal and she has lodged an appeal with the full bench of the Federal Court.

Four months ago Lee's claim was rejected by the tribunal and she has now been in detention seven months, but her optimism remains. "When I first came here I was depressed," she says. "I wanted to go home to Mum. I even booked an airline ticket. Then I decided to stay and fight.

"I had a girlfriend on the outside who used to visit me, but she went back to China a week after I was detained. When she returned, she dropped me. Most of the Lima Dorm ladies are older, some are in their 50s; they are just like my mum, they care for me.

"I am not locking myself into my room. I have a long battle to go."

For all those inside the wire at Villawood, the threat of sudden deportation hangs heavy over their heads. The screams of Wang Meihui on March 28 only crystallised the fear they already shared.

Since Wang Meihui was forcibly repatriated refugee advocates in Australia have been unable to contact her. Her husband says she has not returned to their village.