The study in the Archives of Paediatrics & Adolescent Medicine is the first to show gambling among children this young, said Linda Pagani, who led the study at Sainte-Justine University Hospital Research Centre and the Universite de Montreal.

"The question has always been, 'What comes before adolescent gambling?'" Pagani said in a telephone interview.

The study's results add gambling to a list of later problems associated with early impulsivity, she said, including delinquency, failure to complete high school and mental health and addiction problems in adulthood.

Kindergarten teachers for 163 students were asked to complete a questionnaire at the beginning of the school year to rank the children's inattentiveness, distractibility and hyperactivity.

Six years later, at an average age of 11.5, the children told the researchers in telephone interviews how often they participated in gambling-related behaviours such as playing cards or bingo, buying lottery tickets, playing video games or video poker for money or placing bets at sporting events or with friends.

After controlling for factors like family composition, parents' education and household income, the researchers found an increase of one unit on the impulsivity scale in kindergarten corresponded to a 25 per cent increase in gambling involvement by the sixth grade.

People who start gambling in adolescence are more likely to have severe gambling problems in adulthood, Pagani said.

"Attention problems are a public health issue," she said.

But Dr Timothy Fong of the Gambling Studies Program and Impulse Control Disorders Clinic at the University of California Los Angeles said parents should recognize that impulsivity and even early gambling do not guarantee that a child will develop a serious problem later in life.

What the new study does provide, Fong said, is more evidence on how gambling disorders develop.