The Causes of ADHD
ADHD (attention-deficit hyperactivity disorder) is a common ‘neurodevelopmental disorder’ which can result in significant functional impairments for the individual and have a detrimental impact on their family’s ability to function effectively.
Neurodevelopmental disorders
A neurodevelopmental disorder is one in which the development of the brain is atypical (or "unusual"), leading to abnormal brain function.
Because they are related to the development of the brain’s nervous system, neurodevelopmental disorders begin in childhood, where most of this development occurs, and tend to last to some degree throughout the lifetime.
Autism spectrum disorders, Tourette’s syndrome, Down syndrome, schizophrenia, dyslexia and conduct disorder are all examples of neurodevelopmental disorders.
Rates of comorbidity between neurodevelopmental disorders are high, meaning that those with ADHD are more likely to have Tourette’s, for example, than the general population.
The brains of those with ADHD develop differently.
There are often delays in the development of key parts of the brain, as well as deficiencies of key hormones (which carry signals between different areas of the brain) in others.
ADHD is one of the most heritable psychiatric conditions.
For many of those with ADHD, the likelihood is that one or both of their parents have the condition.
Inheritance of ADHD symptoms
We are still in the early stages of understanding the development and functioning of the brain. There is no single gene we know of that causes ADHD; what we do know is that the genetic processes that lead to you “inheriting” your father’s height or your mother’s nose also make it likely that your brain might develop in a similar way.
In 2018 the scientific journal Nature published a “meta-analysis” (a summary study of relevant research) of the genetics of ADHD, including recent research into the heritability of the condition. Click here to read the study.
While we know that the brains of those with ADHD have developed differently, there is also evidence that environmental impacts can have a significant impact on the symptoms of those with ADHD.
The field of ‘epigenetics’ explains the relationships between genetic and environmental factors in an individual’s development.
Environmental factors
The ADHD Foundation has prepared a useful guide to environmental risk factors associated with ADHD, including pregnancy risk factors, socio-economic risk factors and environmental contaminants.
While none of the following can be proven to cause ADHD, research internationally has demonstrated connections between the severity of an individual’s ADHD symptoms and quality of their diet, sleep and exercise.