“We found that teenagers who reported being frequently bullied were twice as likely to be clinically depressed at 18 years,” said Lucy Bowes, PhD, a researcher at the University of Oxford in England, who led the research.
The researchers found an association, not a definitive cause-and-effect relationship, Bowes said. “In our type of study, we can never be certain that bullying causes depression,” she explained. “However, our evidence suggests that this is the case.”
To explore the possible link, the investigators used data on nearly 4,000 teens in the Avon Longitudinal Study of Parents and Children, a community-based group born in the United Kingdom. At age 13, all completed a questionnaire about bullying. At 18, they were assessed for depression.
The study found that nearly 700 teens said they had been bullied “often” — more than once a week — at age 13. Of those, nearly 15% were depressed at age 18. More than 1,440 other teens reported some bullying — one to three times over a six-month period — at age 13. Of these, 7% were depressed at age 18. In comparison, only 5.5% of teens who weren’t bullied were depressed at age 18.
Bowes also found the often-bullied teens tended to stay depressed longer than others. For 10% of those often-bullied who became depressed, the depression lasted more than two years. By comparison, only 4% of the never-bullied group had long-lasting depression.
Among the bullying tactics, name calling was the most common type, experienced by more than one-third of the teens. About one of four had their belongings taken. About 10% were hit or beaten up. Most never told a teacher and up to half didn’t tell a parent. But up to three-quarters did tell an adult if the bullying was physical, according to the study published in the online edition of the BMJ.
Bowes noted that other studies have found the same bullying-depression link. If it does prove to be a causative factor, she added, bullying may account for 30% of those who develop depression in early adulthood.
Bowes L, et al. Peer victimisation during adolescence and its impact on depression in early adulthood: prospective cohort study in the United Kingdom. BMJ. 2015; 350:h2469.