Woodbridge Hospital began as a 30-bed building at the corner of Bras Basah Road and Bencoolen Street in 1841. It was then known as The Insane Hospital. It was renamed the Lunatic Asylum in 1861, and moved to a site near the old Kandang Kerbau Maternity Hospital, and then to Sepoy Lines in 1887. Relocated for the last time to Yio Chu Kang in 1928, it became known as The Mental Hospital.
For a brief period from 1945 to 1947, the British Royal Air Force from the nearby Seletar Airfield requisitioned the hospital for use to treat the sick and wounded of Allied servicemen and Japanese POWs after the end of hostilities of World War 2. Thus, the female section was converted into the RAF Hospital while the male section was allocated for use as the Japanese Prisoners of War Hospital. It was known as the 81 Mobile Field Hospital until it's return to normal civilian usage in 1947, this hospital was the first Royal Air Force hospital established after the Japanese surrender.
In the 1970s, the then Woodbridge Hospital faced serious resource shortage problems in every aspect. Equipment and facilities were old and in poor condition, and the 80-ha hospital environment felt more like a prison with its fenced-up corridors, grilled gates and barred windows. Associate Professor Teo Seng Hock, Woodbridge's medical director from 1979 to 1996 was quoted in IMH's latest publication Heartening Minds for saying that it was quite intimidating or frightening just to walk from one ward to another, especially during the night. The hospital had only 15 doctors caring for 2500 patients, and as a result only patients with the most serious cases were referred to Woodbridge. It was also widely-known that doctors resigned upon being posted there. The patients did not have enough pyjamas to wear, and had to be given used police uniforms as substitute wear. In 1993 the hospital was relocated to the new premises at Buangkok Green Medical Park in Hougang. With the move came with changes in medical care, focusing from custodial care to community care. This means having patients being assessed and treated in a way that can help them re-integrate into society more easily.
In 2002 The Institute started a trial programme to shift 500 mainly-schizophrenic patients who have been with the Hospital for many years, but are mentally stable after treatment and regular medication, to Pelangi Village. The Village comprises six homes and a central activity centre for the mentally ill and destitute in Buangkok Green, and set up by the Ministry of Community Development, Youth and Sports. These homes will be managed by seven voluntary welfare organisations (VWOs) caring for these patients and their activities in the Village. The VWOs will set up operations within the IMH campus, and assist IMH doctors in monitoring their conditions and their medication in the Village. The initiative saw great success which helped to lessen the workload by their medical staff, so that they can engage in preventive programmes in the community. These programmes include detecting and prevent mental illness early, and preventive services for existing patients such as home care services for patients who default on treatment, and treatment in polyclinics and satellite clinics.
In April 2006, the Woodbridge Hospital compound was marked as Singapore's 83rd historic site by the National Heritage Board (NHB). IMH also set up a museum to showcase artefacts from the hospital's history. The site was marked and the museum officially opened by Minister for Health Khaw Boon Wan on 10 April 2006.
Today, The Institute of Mental Health sits on a sprawling 450,000 square metre site in the Buangkok Green Medical Park at Buangkok since its establishment in 1993. It houses 1,700 in-patients under the care of 80 doctors, and takes on a proactive approach to helping people deal with mental problems. The Institute runs an eight-week in-patient rehabilitation programme coaching patients to deal with everyday life problems, to socialise and how to conduct themselves at job interviews. They have also undertaken a national drive to educate the public and de-stigmatise mental illness, by running public awareness campaigns at shopping malls and working with school counsellors and voluntary welfare groups to spot problems early with their wards.