The impact of childhood bullying can affect people up to four decades later.
The startling finding has emerged in a study of almost 8,000 people born during a single week in 1958 and whose parents provided information that the children were bullied between the ages of seven and 11 years.
The children were followed up until the age of 50.
The study showed that the negative social, physical and mental health effects of childhood bullying were still evident nearly 40 years later.
Individuals who were bullied in childhood were more likely to have poorer physical and psychological health and cognitive functioning at age 50.
Those subjected to frequent bullying were at an increased risk of depression, anxiety disorders, and suicidal thoughts.
They were also more likely to have lower educational levels, with men who were bullied more likely to be unemployed and earn less.
The study found that social relationships were also affected and those who had been bullied were less likely to be in a relationship, have good social support and were more likely to report a lower quality of life and life satisfaction.
The study of childen in England, Scotland and Wales showed over a quarter of the children (28pc) had been bullied occasionally and 15pc were bullied frequently – similar to rates in the UK today.
Professor Louise Arseneault, from the Institute of Psychiatry at King’s adds: “We need to move away from any perception that bullying is just an inevitable part of growing-up.
“Teachers, parents and policy-makers should be aware that what happens in the school playground can have long-term repercussions for children.
“Programmes to stop bullying are extremely important, but we also need to focus our efforts on early intervention to prevent potential problems persisting into adolescence and adulthood.”
Bullying is defined as repeated hurtful actions by children of a similar age, where the victim finds it difficult to defend themselves.
The harmful effect of bullying remained even when other factors including childhood IQ, emotional and behavioural problems, parents’ socioeconomic status and low parental involvement, were taken into account.
Details of the British National Child Development Study are published in the American Journal of Psychiatry.