About one in 20 children are diagnosed with attention deficit hyperactivity disorder (ADHD) at some point during their school life. Interestingly, for every girl diagnosed, there are between three and seven boys who receive an ADHD diagnosis.
Children and adolescents who are affected by ADHD have difficulty with things like sitting still, organisation and concentrating on work. These and other symptoms often make the school environment hard to cope with, and have a negative impact on academic achievement, relationships, and future employment opportunities. Some children do grow out of their ADHD symptoms, but many continue to experience problems as adults.
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Though medication has been developed to relieve the symptoms, little is known about ADHD's exact causes. Our biggest clue has come from family studies – particularly those comparing ADHD symptoms in identical and fraternal twins – which have long indicated that ADHD is largely genetic. And recently, groundbreaking research has begun to identify the specific genetic risk factors related to ADHD, and to reveal the complexity of the condition. We now know that thousands of different genetic risk factors – including common variants in genes known to affect healthy brain development – collectively contribute to increase the risk of ADHD. But it is still not yet clear why there is a gender difference in prevalence.
There are many theories as to why ADHD is more commonly diagnosed in boys than girls. One possibility is that girls are in some way "protected" from developing ADHD, and so it takes a higher burden of risk factors than in boys for girls to develop problems. Another possibility is that ADHD symptoms are missed in girls or that mental health problems in girls develop into problems other than ADHD.