About 59 per cent of participants had experienced some peer victimisation in the first years of elementary school.
Teens who were severely bullied as children by peers are at higher risk of mental health issues, including suicidal thoughts and behaviours, a study has found.
"Our findings showed a general tendency, in about 15 per cent of the children, of being exposed to the most severe levels of victimisation from the beginning of their education until the transition to high school," said Marie-Claude Geoffroy from McGill University, Montreal in Canada.
"Those children were at greater risk of debilitating depressive/dysthymic symptoms or anxiety and of suicidality in adolescence than less severely victimised children, even after we accounted for a plethora of confounders assessed throughout childhood," said Geoffroy.
The study, published in the Canadian Medical Association Journal, looked at data from 1,363 children born in 1997-98 who were followed until age 15 years.
Researchers assessed children, based on self-reporting about peer victimisation, at ages 6, 7, 8, 10, 12 and 13 years.
Participants came from a range of socioeconomic backgrounds, family structures, with slightly more females (53 per cent) than males.
They were categorised into none/low victimisation, moderate victimisation and severe victimisation.
Children who experienced severe peer victimisation were more than twice as likely to report depression or low moods at age 15 compared with those who experienced low or no victimisation, and three times more likely to report anxiety.
Most troubling, the severe victimisation group was almost 3.5 times more likely to report serious suicidal thoughts or suicide attempts compared with the none/low group.
Children who experienced moderate victimisation were not at increased risk of reporting mental health problems.
About 59 per cent of participants had experienced some peer victimisation in the first years of elementary school, although it generally declined as the children grew older.
"Although peer victimisation starts to decrease by the end of childhood, individuals in the severe trajectory group were still being exposed to the highest level of victimisation in early adolescence," researchers said.
"Our results suggest that severe peer victimisation may contribute to the development of mental health problems in adolescence," they said.
"Therefore, it is important to prevent severe victimisation early in the lifespan," they added.
Researchers add urge starting antibullying initiatives before children enter school.
The researchers note self-reporting of victimisation as a study limitation.