A condition which makes people lash out violently for no reason is vastly under-diagnosed, say US researchers.
IED may be more common than previously thought
As many as 16 million Americans have been affected by intermittent explosive disorder (IED) in which the sufferer displays unwarranted violent outbursts.
A study in Archives of General Psychiatry showed 4% of the US population had severe IED with three or more outbursts in the past year.
An expert said cultural differences in the UK could mean its rate was lower.
IED is clearly defined in the manual of mental disorders (DSM-IV) but no-one really knows how many people might be affected by the disorder.
To be diagnosed with IED, an individual must have had three episodes of impulsive aggressiveness which are grossly out of proportion to the situation, such as that seen in cases of road rage or domestic violence.
The person must lose control suddenly and break or smash something, hit or try to hurt someone, or threaten to hurt someone.
Researchers from Harvard Medical School and Chicago University assessed results of a national face-to-face survey of 9,282 US adults which was carried out between 2001 and 2003.
They found that 7.3% of the population could be classed as having IED, as they previously had three or more aggressive outbursts - a much higher rate than previously estimated.
Around eight million adults had the most severe form of IED, with much more frequent outbursts.
Overall, the average person with IED will carry out 43 attacks, the study suggested.
IED tends to first manifest itself during adolescence, with the average age of the first episode found to be 14 years of age.
Although most study respondents had seen a professional for emotional problems, only 12% had been treated for their anger in the past 12 months and only 29% of people had ever received treatment for the condition.
Dr Ronald Kessler, study leader, said: "IED is not a clinical term well-known in society, but the weight of these numbers should help patients and physicians come to recognise the pervasiveness of this disorder and develop appropriate treatment strategies."
Co-author, Professor Emil Coccaro added: "In the general population, aggressiveness or 'blowing up' is considered bad behaviour.
"But IED goes beyond that, having strong genetic and biomedical underpinnings.
"If people think these explosive outbursts are just bad behaviour, they are not thinking of this problem as a serious biomedical problem that can be treated."
The researchers concluded that given the early onset IED, identifying the condition early, perhaps through violence prevention strategies in schools and providing treatment, might prevent later associated problems such as alcohol and drug dependency and depression.
Dr Deenesh Khoosal, spokesperson for the Royal College of Psychiatrists and consultant psychiatrist at Leicester General Hospital said IED was a very carefully defined syndrome.
"There must be several discrete episodes so it can be a fairly long standing issue and it has to be terribly out of proportion.
"You also have to exclude other things for example antisocial personality disorders.
But he added that the prevalence seemed "pretty high".
"In the UK that would extrapolate to a lot of people, although there are cultural factors which could have an effect - we wouldn't confront someone who was ranting and raving and we don't have the same gun culture," he said.