Researchers analysed data from between 1996 and 2006 from the NHS Information Centre, the Department of Health and the 2006 ‘Count me in’ census.
Total psychiatric admissions fell from a high of 214,000 in 1998 to 183,699 by the end of the study period.
But the number of involuntary admissions increased from 42,822 in 1996 to 51361 (20%) in 2006.
Overall the proportion of NHS beds occupied by patients admitted under a section of the mental health act increased from 23% in 1996 to 36% in 2006.
Patients were also three times more likely to be admitted to a private psychiatric facility
The research said a change in case-mix towards psychotic, alcohol and substance misuse disorders has changed the environment on inpatient psychiatric wards.
Scott Weich, professor of psychiatry at Warwick Medical School’s Health Sciences Research Institute, said: ‘Findings provide further evidence of the rising number of involuntary admissions and the changing, more morbid, composition of inpatient populations.’