Nine per cent of people with epilepsy died young compared with just 0.7 per cent of those without the condition, the 41-year research discovered.
And the findings, published in The Lancet, showed that people with both epilepsy and alcohol or drug disorders were 22 times more likely to die than someone who did not have either.
Someone who has epilepsy is also four times more likely to commit suicide than someone who does not, the team from Oxford University said.
Only half of the UK’s 600,000 epilepsy sufferers are seizure-free, and one in 20 people will have an epileptic seizure at some point in their life.
Dr Seena Fazel from Oxford University, who led the study, said standard checks could help reduce the risk of premature deaths in people with epilepsy.
Dr Fazel commented: "Our results have significant public health implications as around 70 million people worldwide have epilepsy, and emphasise that carefully assessing and treating psychiatric disorders as part as part of standard checks in persons with epilepsy could help reduce the risk of premature death in these patients.
"Our study also highlights the importance of suicide and non-vehicle accidents as major preventable causes of death in people with epilepsy."
The study, which tracked 69,995 people with epilepsy born in Sweden between 1954 and 2009 for a 41-year period, found suicides and accidents accounted for almost 16 per cent of all deaths in people with epilepsy.
Of these, three-quarters also had been diagnosed with a psychiatric condition such as depression. They were the most common cause of death not linked to the underlying disease process.
The researchers also found that the risk of premature death in people with epilepsy compared similarly to their unaffected siblings and the general population. This suggests that epilepsy is an independent cause of early deaths, the academics said.
Simon Wigglesworth, deputy chief executive of Epilepsy Action, said the study was cause for concern.
"The findings of this research are concerning and highlight the need for excellent healthcare for people with epilepsy", Mr Wigglesworth said.
"Getting the best possible support and treatment is important to help to reduce the likelihood of people with epilepsy experiencing mental illness. And a holistic approach to managing the condition should help ensure that people with epilepsy get the best possible treatment for both their epilepsy and any associated conditions.”
A separate study published last week warned that children whose mothers take anti-epilepsy drugs during their pregnancy face an increased risk of developing autism.
By the age of three, children were four times more likely to show traits associated with autism if their mothers had taken drugs to control their epileptic seizures.
According to Epilepsy Research UK, around two-thirds of epileptic seizures can be successfully treated with anti-epileptic drugs.
In the latest study, the causes of death were compared with 660,869 people of the same age and sex from the general population, and 81,396 unaffected siblings of people with epilepsy, to account for the potential influence of genetic or environmental factors.
While in some 60 per cent of cases the cause for epilepsy is not known, some types are inherited and common causes are brain damage, scarring of the brain tissue, a tumour, or chemical and hormonal imbalances in the body.
Epilepsy is a neurological condition defined as the tendency to have recurrent seizures. There are around 40 different sorts of seizure and a person can suffer from more than one type.
Every day 87 people in the UK are diagnosed with epilepsy, and many people who develop epilepsy when they are below the age of 20 will “grow out of it” in adult life, according to Epilepsy Action.
While only 52 per cent of people with epilepsy in this country are seizure-free, the charity estimates that with the right treatment seven in 10 could avoid seizures.
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