Oxford researchers say their figures on life expectancy should galvanise governments and health and social services to put a much higher priority on how mental health services can prevent early deaths.
Mental health has not seen the same public health priority as smoking, say the Oxford scientists, despite these stark figures and the similar prevalence of mental health problems.
One in four people in the UK will experience some kind of mental health problem in the course of a year, it is estimated. Around 21% of British men and 19% of women smoke cigarettes.
The Oxford University researchers report their findings in the open access journal World Psychiatry. The study was funded by the Wellcome Trust.
The researchers searched for the best systematic reviews of clinical studies which reported mortality risk for a whole range of diagnoses – mental health problems, substance and alcohol abuse, dementia, autistic spectrum disorders, learning disability and childhood behavioural disorders. Twenty review papers were identified, including over 1.7 million individuals and over 250,000 deaths.
They repeated searches for studies and reviews reporting life expectancy and risk of dying by suicide, and compared the results to the best data for heavy smoking.
The average reduction in life expectancy in people with bipolar disorder is between nine and 20 years, while it is 10 to 20 years for schizophrenia, between nine and 24 years for drug and alcohol abuse, and around seven to 11 years for recurrent depression.
The loss of years among heavy smokers is eight to 10 years.
All diagnoses studied showed an increase in mortality risk, though the size of the risk varied greatly. Many had risks equivalent to or higher than heavy smoking.
Dr Seena Fazel of the Department of Psychiatry at Oxford University said: ‘We found that many mental health diagnoses are associated with a drop in life expectancy as great as that associated with smoking 20 or more cigarettes a day.