What is the story?
The threatening behaviour characteristic of road rage is actually a symptom of a psychiatric disorder, according to media reports.
The media has claimed that drivers who tailgate the car in front and shout at other drivers are probably suffering from intermittent explosive disorder (IED), a condition that causes people to lash out violently.
This condition, which causes domestic violence and road rage, has been under-diagnosed. It affects more people than illnesses such as schizophrenia and bipolar disorder, reports said.
A person suffering from IED will carry out an average of 43 attacks during their lifetime and will cause £730 worth of damage to property, the papers reported.
What is the research?
The media reports are based on a study which found that the prevalence of IED in the US was much greater than realised.
Researchers used data from a national survey of 9,282 people aged 18 years and older, carried out in 2001-2003, to estimate the US prevalence of IED.
The survey involved face-to-face interviews which included assessment for IED as defined by the US Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).
IED has always been included in the DSM as an impulse disorder distinct from other psychiatric conditions. However, it is not included in the 10th edition of the WHO's International Statistical Classification of Diseases and Related Health Problems (ICD-10), which is usually used for making psychiatric diagnosis in the UK.
Under DSM-IV, a diagnosis of IED requires discrete episodes of 'failure to resist aggressive impulses' resulting in assault or destruction of property.
The aggression must be 'grossly out of proportion to any precipitating psycho-social stressor' and it must also be unrelated to alcohol or drug abuse, or any other medical condition.
The researchers found that 7.3 per cent of the sample population met the DSM-IV criteria for a diagnosis of IED, reporting at least three aggressive episodes during their lifetime.
This is a higher prevalence than expected based on previous research.
The majority had at least one other psychiatric disorder, including depression and substance abuse disorders.
Although 60 per cent had received treatment for emotional problems at some point in their life, only 29 per cent were ever specifically treated for IED.
Most people with IED reported that their first attack of aggression occurred in adolescence. The average age of onset of IED was 14 years.
This is younger than previously suggested, and indicates that IED precedes the onset of other psychiatric illness in most patients.
What do the researchers say?
Lead researcher Dr Ronald Kessler from the Department of Health Care at Harvard Medical School said that early identification and treatment of IED might help prevent the onset of secondary disorders in many cases.
'People with this disorder may be more susceptible to other disorders because of increased stressful life experiences as a result of their disorder, such as financial difficulties or divorce,' he said.
By treating IED early, these negative life experiences could be prevented and the development of further psychiatric conditions averted, he suggested.
Another researcher, Dr Emil F Coccaro, from the Clinical Neuroscience and Psychopharmacology Research Unit at the Pritzker School of Medicine at the University of Chicago, said that treatment for IED should involve SSRI therapy, cognitive behavioural therapy (CBT) or both.
'Ideally, people should be treated with both medicine and CBT,' he said.
What do other experts say?
However, Dr Deenesh Khoosal, consultant psychiatrist at the Leicester Nuffield Hospital, said the prevalence of IED found in this study was very high, and that offering SSRIs to everyone who met these IED criteria would lead to over treatment.
'Nothing like the 7 per cent identified here would really benefit from SSRIs or CBT,' he said.
He added around 0.5 per cent of people in the UK were estimated to have either an explosive personality disorder or psychopathic disorder.
Arch Gen Psych 2006; 63: 669-78
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- A US study has found that around 7 per cent of Americans have intermittent explosive disorder (IED).
- This figure is much higher than previous estimates.
- Not everyone who loses their temper while driving would meet the criteria for IED.
- Researchers say that treating IED with SSRIs or CBT could prevent development of depression.
- The prevalence of psychiatric disorders leading to violent outbursts in the UK is estimated to be 0.5 per cent.
WHAT THE PAPERS SAID
"Anger syndrome 'under diagnosed'"
"Road rage? It's an 'explosive illness'"
The Daily Telegraph
"Scientists find disorder that leads to road rage"