Attention deficit hyperactivity disorder (ADHD) tends to run in families and appears to have a strong genetic link.
While researchers acknowledge that some genetic variants increased a person’s risk of ADHD, they do not fully understand whether some genes require environmental triggers to switch on.
Furthermore, due to the complexity of the condition, researchers are yet to discover a causal relationship with a particular gene or set of genes. This implies that a person’s environment also has a significant effect on how likely they are to develop ADHD.
What is ADHD?
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When a person has ADHD, they find it difficult to pay attention to tasks they do not find stimulating.
This often leads to them making careless mistakes and having difficulty coping in situations requiring continuous mental effort. ADHD can present in various ways, but children and adults generally tend to experience the following symptoms.
The symptoms of ADHD in a child may include:
- daydreaming frequently
- forgetting things
- fidgeting a lot
- taking unnecessary risks
- giving in to temptation easily
- being unable to wait their turn
ADHD in an adult may present as:
- making careless mistakes at work
- getting up a lot and walking around
- talking excessively
- finding it hard to follow instructions
- losing things easily
- experiencing constant distractions
- interrupting people a lot
In children, there may also be differences in the way symptoms present between girls and boys.
It is also important to note that while ADHD comes with challenges, there are also numerous possible benefits.
Is ADHD genetic?
A person whose parents or siblings have ADHD has a higher risk of experiencing symptoms. That said, some people never develop ADHD despite having a family history of the condition.
In fact, twin studies never demonstrate 100% heritability of ADHD, which suggests that a person’s environment also influences how likely they are to develop ADHD.
ADHD brain structure and function
Researchers have observed differences in brain structure between people with and without ADHD.
Children with ADHD tend to have a small frontal lobe. As the frontal lobe is responsible for problem-solving, attention, and decision-making, this could explain why children have problems concentrating and acting on impulse.
Furthermore, the frontal lobe can take longer to develop in some children, which may explain why some people experience fewer or different ADHD symptoms as they get older.
Other frontal lobe functions include:
- language
- judgment
- planning
- delaying gratification
- time perception
- emotion regulation
Neuronal networks, which are groups of connected nerve cells, also behave differently in people with ADHD, particularly networks related to reward and planning.
Other neuronal networks that are different in people with ADHD relate to:
- focus
- attention
- movement
- switching attention between tasks
There are also two neurotransmitters that appear to be lower in people with ADHD: dopamine and norepinephrine. Medications that treat ADHD focus on stimulating the brain and increasing the levels of these neurotransmitters.
Because ADHD is a complex condition, researchers are yet to fully understand exactly why these differences in brain structure cause it.
ADHD risk factors
While a family history of ADHD could increase someone’s risk of developing the condition, other risk factors can play a significant role.
Other ADHD risk factors include:
- brain injury
- exposure to lead at a young age or while in the womb
- exposure to alcohol and tobacco while in the womb
- premature birth
- low birth weight
Controversially, some people believe that eating too much sugar or watching too much television causes ADHD. However, research does not support these beliefs.
ADHD symptoms
There are three types of ADHD, and each has different symptoms.
Predominantly inattentive presentation
If a person has this type of ADHD, they will find the following more difficult:
- organizing or finishing tasks
- paying close attention to detail
- listening to other people talking
- blocking out distractions
- maintaining a routine
Predominantly hyperactive-impulsive presentation
If a person has this type of ADHD, they will find the following more challenging:
- sitting still
- talking quietly
- resisting temptation
- listening and not interrupting
- controlling impulsivity
Combined presentation
If a person has this type of ADHD, they will have a combination of symptoms from the two presentations.
Diagnosis
When a doctor is diagnosing a person with ADHD, they will follow the guidelines from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This ensures that everyone receives the same standard of care.
During the consultation, the doctor will want to talk about the symptoms a person is experiencing and their family medical history to understand if any close relatives live with ADHD.
If they are diagnosing a child, they may wish to speak with the child’s teachers and caregivers to get a sense of their behavior in different environments.
To diagnose a specific presentation of ADHD, a doctor will note how many symptoms fall into the inattention category and the hyperactivity and impulsivity category.
If someone has an equal number of symptoms in each category, they may receive a combined type ADHD diagnosis.
Treatment
The treatment for ADHD usually includes a mixture of therapy and medication.
Medication
A doctor will usually prescribe stimulants to increase focus and attention. However, in some cases, people may experience unwanted side effects, so doctors may recommend non stimulant medication instead. This type takes longer to work but has the same effect of improving focus and attention.
Therapy
Therapy is an effective treatment that can help a person with ADHD and their family better understand their condition.
The types of therapy that a person may receive include:
- behavioral therapy
- cognitive behavioral therapy (CBT)
- parent management training
- stress management techniques
- accommodations at school, such as extra time on tests or time to move around
Summary
ADHD tends to run in families, which strongly suggests that genes play a role in the likelihood of a person developing the condition.
However, it is important to remember that a family history of ADHD does not necessarily mean that a person will inherit ADHD — it just puts them into a higher risk category.
Other risk factors for ADHD include brain injury and exposure to lead, which suggests that a person’s environment is also a significant risk factor alongside a family history of the condition.
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