Attention deficit hyperactivity disorder (ADHD) tends to run in families. Doctors who treat those with ADHD believe there may be a strong genetic link. However, while science has determined that some genetic variants raise the risk of having ADHD, researchers have not determined if environmental factors switch those genes on. Plus, scientists have not discovered a causal link with a specific gene. This means that an environmental trigger is likely necessary to causing ADHD.
What is ADHD?
ADHD stands for attention deficit hyperactivity disorder. A person who has it has difficulty focusing and staying on task. They may be able to focus well on tasks they find stimulating. This can lead to careless mistakes and difficulty coping in situations that require focus such as school or work. ADHD presents in 3 main categories:
ADHD, combined type. This, the most common type of ADHD, is characterized by impulsive and hyperactive behaviors as well as inattention and distractibility.
ADHD, impulsive/hyperactive type. This, the least common type of ADHD, is characterized by impulsive and hyperactive behaviors without inattention and distractibility.
ADHD, inattentive and distractible type. This type of ADHD is characterized predominately by inattention and distractibility without hyperactivity.
A person with ADHD will typically experience all or some of these symptoms on a regular basis:
- 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
When present in children, the symptoms tend to vary between boys and girls. It is also important to note that ADHD can have some positive benefits.
Is ADHD genetic?
A person who has a parent or sibling with ADHD has a higher risk of developing symptoms. However, many people have a family history of ADHD, yet they do not develop symptoms. In fact, twin studies have never demonstrated 100% heritability of ADHD, which implies that environmental factors do play a role.
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 smaller frontal lobe. The frontal lobe is responsible for decision-making, attention, and problem-solving. This may explain with children with ADHD have difficulty focusing and tend to act on impulse. In addition, the frontal lobe may take longer to develop in some children, which may be the reason why ADHD symptoms sometimes decrease as a child grows up.
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 behave differently in people with ADHD are responsible for:
- 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:
- 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
Some people assert that eating too much sugar or too much screen time causes ADHD. Existing research does not support these beliefs.
ADHD symptoms
As noted above, doctors categorize ADHD into three main types:
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 of ADHD
Only a doctor may make a diagnosis of ADHD. It is important to note this as sometimes school teachers will suggest a child may have the condition.
A doctor will follow the guidelines from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This helps to ensure consistent diagnosis and treatment. It also helps because there is no test such as a blood test to make the diagnosis of ADHD.
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 the doctor is diagnosing a child, they may ask the child’s caregivers and teachers for input on the child’s behaviors in varying 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 combination 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
Final thoughts
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.