Teenagers who are bullied by their peers are at high risk of developing clinical depression as young adults, new research suggests.
A study conducted by investigators at Oxford University in the United Kingdom showed that individuals who reported being bullied frequently at age 13 years were about twice as likely to suffer from depression at age 18 compared with their peers who did not experience bullying.
"Our findings suggest that a substantial proportion of the burden of depression in the early adult years may be attributed to peer victimization, assuming that this is a causal relationship," lead investigator Lucy Bowes, PhD, told Medscape Medical News.
"Our study also suggests that the majority of teenagers do not tell parents or teachers if they are being bullied. There are effective interventions to reduce peer victimization, particularly in secondary schools, and these should be refined and evaluated to determine whether this reduces rates of depression," Dr Bowes said.
The study was published online June 2 in the BMJ.
Twice the Risk
The investigators analyzed data on bullying at age 13 years and on depression at age 18 years in 3898 participants in the Avon Longitudinal Study of Parents and Children (ALSPAC), a UK community-based birth cohort study. Participants completed a questionnaire on bullying at age 13 and were assessed for depression at age 18.
Of the 683 teenagers who reported frequent bullying (at least once weekly) at age 13 years, 14.8% met ICD-10 diagnostic criteria for depression at age 18 years. Of the 1446 teenagers who reported some bullying at age 13 (1 to 3 times during a 6-month period), 7.1% were depressed at 18 years. Only 5.5% of teenagers who did not experience bullying were depressed at 18 years.
Roughly 10% of frequently bullied teenagers reported experiencing depressive symptoms for more than 2 years, compared with about 4% from the nonbullied group.
Compared with children who were not bullied, those who suffered frequent bullying by peers had more than a twofold increased likelihood of being depressed at age 18 (odds ratio [OR], 2.96; 95% confidence interval [CI], 2.21 - 3.97; P < .001). The association was only slightly reduced when adjusted for confounding factors (OR, 2.32; 95% CI, 1.49 - 3.63; P < .001). Both sexes were equally at risk.
"Given what we already know about bullying and other adverse health outcomes, we had anticipated that we would find a link between peer victimization in the teenage years and clinical depression," Dr Bowes told Medscape Medical News.
"What was surprising," she said, "was the proportion of depression that might be explained by peer victimization if this really is a causal relationship ― nearly 30% in our sample. Equally surprising and indeed concerning was the proportion of teenagers who reported that they never told parents or teachers about their experience of having been bullied (24% to 74%)."
Time for Action
In an accompanying editorial, Maria M. Ttofi, PhD, from the University of Cambridge, United Kingdom, said the findings in this study are "in line with, and also complement, existing research."
Peer victimization "significantly predicts depression, and societies need to take measures to protect vulnerable young people," she writes. The study offers "clear antibullying messages that should be endorsed by parents, schools and practitioners internationally."
The finding that many children fail to report bullying means parents and teachers need to proactively ask children about school experiences beyond academics, Dr Ttofi noted.
"Future research should aim to establish the causal mechanisms that link peer victimization to depression, thus enabling program planners to move towards theoretically driven intervention strategies," she concluded.
The study was supported by the Wellcome Trust. The authors and Dr Ttofi report no relevant financial relationships.
Medscape Medical News © 2015 WebMD, LLC
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Cite this: Teen Bullying Accounts for Large Share of Adult Depression - Medscape - Jun 12, 2015.