Being unpopular with your classmates may not only make your schooldays miserable, it could also make you ill decades later.
Research has shown the those who are socially isolated in their teens are more likely to suffer health problems from obesity to high blood pressure when they hit their 40s.
The legacy of unhappy schooldays was particularly noticeable among the women studied.
Importantly, the health effects weren't limited to those who were bullied at school, suggesting that even being slightly socially isolated can be harmful to health.
Swedish researchers analysed data from a study that tracked the health and habits of around 900 16-year-olds for 27 years.
At the start, their teachers were asked to rate how extroverted or introverted they were and their popularity. At around the age of 43, they underwent a battery of medical tests.
The results linked unpopularity and social isolation to obesity, high blood pressure, diabetes, bad blood fats and lack of 'good' cholesterol. This cluster of problems is known as metabolic syndrome and greatly increase the risk of heart attacks and strokes.
The study, published in the journal PLoS ONE, also showed that the more unpopular someone was in their teens, the more likely they were to suffer from metabolic syndrome in middle-age.
The effect was particularly noticeable among the girls, with the most unpopular and introverted at 16 more than three times as likely to be in bad shape at 43.
The researchers, from Umea University, said the results can't simply explained away by those who are in bad health in middle-age being sickly since their teens.
They added that their study is the first to show that unhappy schooldays can have such long-lasting consequences.
Various factors could lie behind the effect. For instance, loneliness raises levels of the hormone cortisol and can push blood pressure up into the danger zone for heart attacks and strokes.
High levels of cortisol can also suppress the immune system, raising a person's vulnerability to disease. The lonely also sleep more fitfully, feel lethargic during the day and are more likely to rely on sleeping tablets.
Those who feel left out may also resort to comfort eating and be less likely to look after themselves in general.
- DAILY MAIL