Is ADHD Hereditary?
When every textbook approach to addressing behavioural problems in a child fails, it may be time to stop looking at family dynamics in the search to find an explanation.
It may be possible that the bad behaviours are in fact signs of an attention deficit disorder; if this is the case, parents can be re-assured that scientists are now reasonably certain that the condition is mostly hereditary. Whilst parenting problems can exacerbate attention deficit and hyperactivity behaviours, they are not the cause of them.In broad terms, ADHD or attention deficit hyperactivity disorder is a condition in which the affected person is likely to act and react to situations without considering the consequences, and this trait is referred to as hyperactivity - impulsiveness.
A person with a deficit disorder may have difficulties making or keeping friends, and may show a high degree of disorganisation and a lack of mental focus in their day-to-day life. In a child, if these problems remain untreated they are likely to affect behaviour as well as social and academic progress at school, with lifelong consequences.Hereditary Conditions
Ever since scientists recognised that ADHD behaviours seemed to run in families, the search has been on to find a cause for familial traits of antisocial behaviour. For a long time, researchers thought that attention deficit disorder could be a perpetuation of the conditions associated with poor parenting skills or social deprivation within less privileged families. Clinical research studies were designed to prove the case one way or the other.What scientists found surprised many people. The studies confirmed that ADHD ran in families who were genetically related, and that it could appear in any family, even those with highly achieving parents. When the researchers questioned and tested parents of children with the disorder, they found that many parents had also had attention deficit problems in their youth.
In other words, many parents had ADHD signs themselves, and these had passed undiagnosed in their childhoods. It was clear that this was one of a number of hereditary conditions, and the search began for a genetic cause for the disorder.Finding the Genes
The strongest evidence for a genetic link to ADHD comes from detailed studies of twins and children who were adopted but whose 'natural' families and siblings could be traced and investigated.A first group of studies looked at the genetics and behavioural traits of both identical and non-identical twins, whilst a second group looked at adopted children and their 'natural' genetically related siblings, as well as the siblings from the adoptive families. The results were conclusive.
Results of Studies
When researchers looked at identical twins where one twin was known to have ADHD, they found that there was a 72 to 83 per cent probability that the other twins would also have ADHD signs. This was true even where twins had been adopted and placed in different families.However, when the researchers contrasted these findings with non-identical twins of the same sex, they found that the probability that both twins would have an attention deficit disorder was reduced to between 21 and 45 per cent.
When researchers included the extended families of ADHD sufferers, they found that parents, siblings and children of people with attention deficit disorders were five times more likely to have the disorder than individuals who were not related to a diagnosed sufferer.
The strongest evidence of a genetic involvement in ADHD comes from a study that found that children of parents with the disorder had a one in two chance of having the condition themselves.
One Gene or Many?
To begin with, researchers believed that there may be a single gene for attention deficit disorder. However, they now think that there are many genes that may predispose someone to developing the disorder; they also believe that there is a range of factors involved that determine whether an individual will go on to show ADHD signs and behaviours.The disorder can skip generations, and can be very mild in some people. Whilst poor parenting skills or poor management of an ADHD child can exacerbate the problems, they are very unlikely to be the primary cause of the disorder.
