Having meningitis as a baby can lead to teenage behavioural problems, researchers have suggested.
The characteristic meningococcal rash
In a survey, almost half of parents with children who had been affected by meningococcal disease said their children had behavioural problems, compared to just one in five parents whose children had not had it.
The researchers, from the Imperial College of Medicine, admit teenage behaviour is complex, but say teenagers affected by meningitis do behave more badly their peers.
The team surveyed the parents and teachers of 739 English and Welsh 13-year-olds who had contracted bacterial meningitis before their first birthday between 1985 and 1987.
The children had previously been studied by researchers looking at meningitis in infancy.
Many people who have had meningitis and septicaemia experience problems with concentration and memory
Linda Glennie, Meningitis Research Foundation
The parents were asked whether their children had emotional problems, and about their behaviour, hyperactivity, peer problems and social skills, using a recognised scale designed to assess behaviour.
Parents and teachers were also asked what kind of impact the child's behaviour had had on the family or the classroom, and whether they had any problems that interfered with their life at home or leisure activities.
The child's illness was classed as "uncomplicated" or "complicated", an infection with a high fever, convulsions or relapse.
Parents and teachers of 606 children unaffected by meningitis as a child were also surveyed.
The teachers were not told which of the teens had had meningitis.
Forty-six per cent of parents whose children had contracted meningitis said their children's behaviour was problematic, compared with only 20% of the other parents.
Parents of those who had had more complicated meningitis were three times as likely to say the illness had had a negative impact on their home or social life.
Teachers said over a third of those who had had meningitis in infancy were "difficult", compared to 23% of those who had not.
The research is published in the Archives of Disease in Childhood.
Writing in the journal, the researchers accepted other factors - such as changes in the child's home circumstances - could have had an effect.
But they added: "This study shows that 13-year-old children who suffered from bacterial meningitis during the first year of life have significantly more behavioural problems than matched controls [unaffected peers] when assessed by parents and teachers."
Linda Glennie, head of research and medical information for the Meningitis Research Trust, told BBC News Online this large study confirmed previous findings.
She said: "Many people who have had meningitis and septicaemia experience problems with concentration and memory.
"These are the types of things that get them labelled as children with problems. And it does impair their educational attainment."
Ms Glennie said parents needed to be aware of the problems their children could suffer, and ensure they received the support and advice they needed.
The Meningitis Research Foundation has a helpline which can be contacted on 0808 800 3344.