But they are almost invisible because they are shut away, and almost ignored because they are a source of shame or fear. In a very poor country, especially one that has had its social fabric ripped apart, this group is clinging to the very edge of existence. In the small Central Asian state of Tajikistan, MSF has been saving hundreds of these lives: the lives of patients in psychiatric institutions.
In the MSF mission there first surveyed the mortality rate in the state mental hospitals and clinics, some of them were losing over 25% of their patients every year. In 1996 in the biggest, national hospital called Leninski in the capital Dushanbe, 176 died. But mental illness is not normally a killer.
These people died from much more banal causes: hypothermia, starvation, pneumonia. The state health system in Tajikistan, heavily subsidised by other parts of the Soviet Union until independence in 1991, had fallen apart. At the bottom of the priorities, in a country further bankrupted by civil war, were the psychiatric institutions. There was no money for food, clothes, heating or hygiene.
Tajikistan is the poorest of the states which emerged from the ruins of the USSR. It has all the classic problems of a centralised, inefficient economy trying to make the transition into a market-driven world. But it also has the legacy of political collapse, as the elites who inherited power have struggled to withstand the armed challenge of nationalist and Islamist dissidents. MSF is there mainly because of that brutal fighting, which saw atrocities on all sides and, in 1997, turned into a heavily armed truce.
Recent elections have not removed the threat of gunfire on the streets of the capital. And the influence of the drug-smugglers from neighbouring Afghanistan has brought mafia-style intimidation, rape and corruption. The crisis in the mental hospitals was just the quietest scream of a wounded society.
Since 1997, MSF has undertaken a programme of rehabilitation of the hospital structures and sustenance of the patients. Dr Nadezhda Velikorodova, the chief of the female department in Leninski hospital, puts it very bluntly today when she says that "So many of my people were dying of hunger and disease that if MSF had not come to help, we would have had to close the hospital. We are still poor and understaffed but at least the institution is no longer a danger to the patients." In 1999, eleven patients died out of 306.
In March this year, MSF handed back the last of the 17 restored institutions to the Ministry of Health. They now have new showers and toilets, safe water supplies, central heating systems and renovated cooking facilities. The kitchens are supplied with staple food items and special dietary supplements for the weakest patients. Blankets, mattresses, clothes and soap continue to save lives alongside the provision of drugs for physical illnesses.
Work on the treatment of the psychiatric conditions is a much tougher proposition. The first steps were to get some vocational therapy to break the hopelessness and immobility of the ward routine. Dr Engels Sattarov is MSF's advisor on care and activities.
"When we started, there was no care provided and no point in having activities because the patients were so weak and so ill," he said. "There's also a problem of lack of trained personnel. So the first priority was to raise the consciousness of the staff."
Now there are reading rooms, a sewing workshop in Leninski, which has a commercial order for 100 mosquito nets and market gardening to produce crops for the hospital.
There is also a programme to connect the medical staff with the Geneva Initiative on Psychiatry, which works to raise professional standards of psychiatric care in former Soviet states. Dr Gulya Ibragimova is MSF's monitor of the relief work. She has noticed an effect on morale among the medical workers that will eventually help the patients.
"There is an increased sense of dignity in the work," she said. "It's difficult to foster when the staff of the Ministry of Health are not getting paid properly. But compared with our first impressions, there is now real motivation."
As part of this process, the MSF team has been working with their allies in the Ministry of Health to shift the political attitudes towards mental health. The whole project has been managed in conjunction with the Ministry, so that they progressively assume responsibility for it.
One major shift has been in the legislation which underpins the medical work. Tajikistan now has a mental health statute before parliament that, according to Kaz de Jong, MSF's Mental Health advisor, "If passed, will be one of the most forward-looking pieces of legislation on this subject anywhere in the region."
As the institutional project reaches maturity, MSF is just starting work on a Community Mental Health project which could help to change some of the public attitudes which have so debilitated psychiatric medicine.
A team of is being trained to work with people traumatised by the horrors of the civil war or suffering from stress brought on by the continued lawlessness and insecurity of everyday life. The project is mounting a public education campaign to raise awareness of mental health issues and to move perceptions away from the traditional hostility and fear.
The work has ambitious, long-term goals for a society struggling to recover from economic and political implosion. But the patients of the psychiatric institutions are already - and literally - living testament to the progress that is possible.