People who were bullied in their teenage years are more susceptible to depression later on in life, new research suggests.
The research, published in the British Medical Journal, says there is a rapid increase in depression from childhood to adulthood and one contributing factor could be bullying by peers.
A team of scientists, led by Lucy Bowes at the University of Oxford, examined the relationship between bullying at 13 years and depression at 18 years.
They analysed bullying and depression data on 3,898 participants in the Avon Longitudinal Study of Parents and Children (ALSPAC), a UK community based birth cohort.
The participants completed a self-report questionnaire at 13 years about bullying and at 18 years completed an assessment that identified individuals who met internationally agreed criteria for depressive illness.
The report said that "of the 683 teenagers who reported frequent bullying at more than once a week at 13 years, 14.8% were depressed at 18 years. And of the 1,446 teenagers who had some bullying of 1-3 times over six months at 13 years, 7.1% were depressed at 18 years.
"Only 5.5% of teenagers who did not experience bullying were depressed at 18 years."
Name-calling is most common form of bullying
Overall, the researchers found, 2,668 participants had "data on bullying and depression as well as other factors that may have caused depression such as previous bullying in childhood, mental and behavioural problems, family set up and stressful life events.
"When these factors were taken into account, frequently bullied teenagers still had around a two-fold increase in odds of depression compared with those who did not experience bullying. This association was the same for both males and females."
The research found that the most common type of bullying was name calling - 36% experienced this, while 23% had belongings taken.
In an accompanying editorial in the BNJ, Maria M Ttofi from the University of Cambridge writes that this study has clear anti-bullying messages that should be endorsed by parents, schools and practitioners. She also calls for more research to establish the causal links between bullying and depression, and to drive specific interventions to reduce victimisation.