The research, published in the Journal of Schizophrenia Research, was carried out by Swansea University Medical School and Cardiff University School of Medicine through the National Centre for Mental Health.

The team analysed data from a UK population of 3.9 million people between 2004-2013, where 29,797 had a diagnosis of a severe mental illness from primary care, outpatients and/ or a hospital admission.

Overall, people diagnosed with a severe mental illness (SMI) were almost three times as likely to die prematurely than the general population.

Professor Ann John of Swansea University Medical School, a Professor of Public Health and Psychiatry, specialises in the prevention of suicide and self-harm. She said the study revealed some statistics that must serve to inform future healthy policy and improve services, both in primary and secondary care.

Professor John said: “We have known for a long time that people with severe mental illness like schizophrenia and bipolar disorder tend to die earlier than those without these chronic conditions, by about 10 to 15 years.

“Many of these deaths are preventable. It’s a clear health injustice. However, it’s important to understand why these deaths occur to develop policy initiatives to improve services and tackle this in an informed targeted way”.

The data shows that compared to the general population, people with severe mental illness are:

• Thirteen times as likely to die from ill-defined and unknown causes.
• Twelve times as likely to die by suicide (21 times as likely if female).
• Eight times more likely to die from substance misuse.
• Five times more likely to die accidentally.
• Four to five times as likely to die from dementia, Alzheimer’s or Parkinson’s.
• Twice as likely to die from cardiovascular disease.
• Three times as likely to die from respiratory disease, particularly pneumonia.

It is already known that people with severe mental illness are at increased risk of dying prematurely, but such a detailed examination of specific types of death has not been carried out until now in those presenting to general practice and/or hospitals. Most studies have previously focused on one setting.

Professor John, who also chairs the National Advisory Group to Welsh Government on Suicide an Self Harm Prevention, added: “We looked across both general practice and hospitals and found that those people with SMI and in contact with their GP were twice as likely to die compared to the general population - but in those admitted to hospital, this rose to three times as likely”.

Where causes of death are common such as cardiovascular disease, even a small increase will affect large numbers of people with severe mental illness so prevention is important. For some less common causes of death such as suicide, the difference compared to the general population makes it an important focus of prevention.

Professor John added: “It is very important that families and friends of people living with severe mental illness encourage their loved ones to engage in programmes which include smoking cessation, drug cessation, increased exercise, healthier eating, maintenance of a healthy body weight and control of high blood pressure/cholesterol.

“But it is equally important that any initiatives aimed at encouraging healthy lifestyle behaviours are targeted and tailored for those with SMI and are available in both primary and secondary care settings - from smoking cessation to social prescribing to group gardening”.

Professor John added that suicide in this group is probably underestimated and that a greater emphasis on suicide prevention in a community setting in this group is needed: “Healthcare professionals in both GP and hospital settings should routinely ask about suicidal thoughts, depression and the misuse of alcohol and drugs, and be able to recommend treatment where appropriate. Liaison psychiatry could be extended to fill the gap between community settings and psychiatry as well as general hospital settings and psychiatry. Investing in educational and psychosocial programmes now will save lives”.