Whereas most of the risk can be attributed to physical illness such as cardiovascular and respiratory diseases and cancer (80% of deaths).
The higher death rate is also normally reported in terms of mortality rates but other measures can be used such as potential years of life lost, average age at death and life expectancy. Life expectancy is also a useful alternative as it can reflect changes in rates across ages.
Of the few studies of life expectancy in people with mental illness, some have reported a gap of 14 years for males and six for females while others a gap of 20 years for males and 15 for females. Little is known on whether life expectancy between people with mental illness and the general population has changed over time. Two different studies have shown different results with one suggesting the gap has increased and one showing a modest narrowing.
Researchers from Australia therefore carried out an analysis of Australian population-registers between 1985 and 2005 to examine the life expectancy gap. They also calculated the contribution of major causes of death including cancer, heart disease, respiratory disease and unnatural causes of death.
Data were taken from population-wide databases covering Western Australia as well as Mental Health Information Systems and Death Registrations.
The researchers compared life expectancy in the cohort of psychiatric patients with life expectancy at birth for the total Western Australia population (published by the Australian Bureau of Statistics).
There were 292,585 people in contact with mental health services in the area between 1983 and 2007 of whom 47,669 (16%) died in the same period. The active prevalence of some mental disorders increased over time including affective psychoses (where people experience a loss of contact with reality) and stress.
In the general population, life expectancy increased from 73 years in 1985 to 79 years in 2005 for males and from 79 to 83 in females. Among psychiatric patients, those with alcohol or drug disorders had the lowest life expectancy in 1985 which exceeded 20 years compared with the general population. For all disorders combined, the life expectancy gap increased from 13 years in 1985 to 15 years in 2005 in males and from 10 to 12 years in females.
Although suicides represented a large proportion of excess deaths for patients with mental illness, physical conditions represent the majority of excess deaths. Cardiovascular disease was the main cause particularly for patients with schizophrenia (32% males, 46% females), other psychoses (33% males, 41% females) and neurotic disorders (38% males, 38% females).
The study demonstrates a widening gap in life expectancy of 16 years for males and 12 years for females: the overall gap has increased by 2.4 years for males and 1.6 years for females since 1985. The researchers believe the increased gap is "largely driven by increasing life expectancy in the general population rather than a reduction in life expectancy in psychiatric patients".
The widest gap in life expectancy was observed in people with alcohol and drug disorders and this was maintained through the period of the study. Substance abuse is a well-established risk for cardiovascular disease and many cancers which makes these findings less surprising.
The researchers add that there have been significant advances in reducing death rates due to common physical conditions, but people with mental illness have not benefited to the same extent as the general population.
The researchers conclude that results show the impact of mental illness on life expectancy. They say that while strategies aimed at the prevention of suicides remain an important component, "80% of excess deaths are associated with physical conditions" and that "multi-pronged approaches will be required to address these inequalities". They also stress that treating both physical health problems and risk factors "would result in improvements to both physical and mental health".
In an accompanying editorial, Graham Thornicroft, Professor of Community Psychiatry at King's College London, says that the paper's findings raise "disturbing" questions about our "disregard for the duration and value of the lives of people with mental illness". He suggests that we need evidence based interventions that can reduce excess mortality such as smoking cessation and lifestyle programmes. Professor Thornicroft concludes that this is a "human rights disgrace" and that "internationally agreed standards" are needed.