Los Angeles, June 7: Road rage drivers who speed, weave through traffic, honk their horns, cut up — and occasionally shoot at — fellow motorists are not simply having a bad day or late for work.

Researchers claim they could suffer from intermittent explosive disorder (IED), a psychiatric condition far more prevalent than previously thought.

Doctors in the US believe 16 million Americans are affected by the disorder, which can trigger outbursts of road rage, tantrums that lead to violent or destructive acts and even domestic abuse.

IED involves multiple outbursts that tend to be “grossly out of proportion to the situation”. It is linked to the inadequate production or functioning of serotonin, a mood and behaviour-regulating chemical in the brain.

The study, published in the Archives of General Psychiatry, claims the disorder appears in adolescence, typically around the age of 14.

Sufferers have an average of 43 attacks during their lifetime resulting in $1,359 worth of property damage. The worst affected cause up to four times as much damage.

The study, conducted by Harvard Medical School and the University of Chicago, found that 7.3 per cent of Americans have IED and 3 per cent the most severe form.

The study is the first reliable indication of the disorder’s prevalence. It affects more people than better-known illnesses like schizophrenia and bipolar disorder, said Emil Coccaro, co-author of the study. “If people think these explosive outbursts are just bad behaviour, they are not thinking of it as a serious problem that can be treated.”

Ronald Kessler, who led the study, said the disorder surprised even mental health
specialists.