Researchers found that children who are rated “highly cheerful” at school went onto die younger than their more reserved class mates.
This is because they are likely to lead more carefree lives full of danger and unhealthy lifestyle choices, it is believed.
They may also be more likely to suffer from mental problems such as bipolar depression which sees moods swing from extreme happiness to debilitating sadness.
Being too cheerful – especially at inappropriate times – can also rouse anger in others, increasing the risk of a person coming to harm.
The study by a variety of universities analysed the details of children from the 1920s to old age.