With more than one in five UK young people saying they’ve recently been bullied, and reports of cyberbullying on the rise, the need to understand the short and long-term impacts it has on mental health is crucial.

An MQ-funded study published today in JAMA Psychiatry has provided the strongest evidence we have to date around direct impact of bullying on the development of mental health problems.

So, what has the research found?

Dr Jean-Baptiste Pingault and his team at UCL found that bullying causes many mental health conditions, such as anxiety and depression, years later.

Previous studies have shown that bullied children are more likely to suffer mental health issues. But it has been unclear whether this is because of the bullying or pre-existing issue like genetic influences or home life – are more likely to explain the relationship. This research provides robust new evidence to demonstrate the causal link.

But the good news is that the results revealed that for some young people these detrimental mental health effects decreased over time, a discovery which could show that children exposed to bullying develop resilience.

How did they find this out?

To gain these unprecedented insights, the researchers surveyed 11,108 participants from the Twins Early Development Study, a longitudinal study collecting data from sets of twins in the UK from early childhood through adolescence.

By using twins, researchers were able to account for the confounding effects of their genes and shared environment because they studied both “identical” twins who have matching genes and home environments and “non-identical” twins, who don’t share all of their genes, but have matching home environments. Both children and their parents filled out questionnaires: at age 11 and 14 they were asked about bullying, and at 11 and 16 they were asked about mental health difficulties.

Researchers found a causal link between exposure to bullying and mental health problems like anxiety, depression, hyperactivity and impulsivity, inattention, and conduct problems. Two years later, the impact of anxiety persisted. Five years later, many of these problems had improved, but 16-year-olds who had been bullied at age 11 remained more likely to have paranoid and disorganised thoughts.

Why does this matter?

This important research is further strong evidence of the need to take the mental health impacts of bullying seriously.

These findings highlight the harmful impact bullying has on mental health, demonstrating the need to intervene early to tackle the issue. It also offers a message of hope – that children can recover and shows the potential of research. We must now research how to create the best support for young people affected by bullying and develop new ways to intervene early and change lives.