Attention-deficit/Hyperactivity Disorder (Demontis, 2018) – Is ADHD genetic?

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Nebula Genomics DNA Report for ADHD

Is ADHD genetic? We created a DNA report based on a study that attempted to answer this question. Below you can see a SAMPLE DNA report. To get your personalized DNA report, purchase our Whole Genome Sequencing!

A sample report on ADHD from Nebula Genomics
A sample report on ADHD genetic variants from Nebula Genomics
To learn more about how Nebula Genomics reports genetic variants in the table above, check out the Nebula Research Library Tutorial.
This information has been updated to reflect recent scientific research as of May 2021.

What is ADHD? (Part 1 of Is ADHD genetic?)

Attention deficit/hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder with onset in childhood and adolescence. It manifests itself through problems with attention, impulsivity, and self-regulation. Sometimes, strong physical restlessness (hyperactivity) is also observed. ADHD occurs in both children and adults. 

The disorder used to be seen as a purely behavioral problem, whereas today, it is increasingly understood as a complex developmental delay of the self-management system in the brain. ADHD can also be understood as extreme behavior that shows a smooth transition to normality. The abnormalities must be very pronounced for the age and consistently present in most situations since childhood. Symptoms alone, however, do not lead to a diagnosis. Usually, only when they severely interfere with lifestyle or lead to recognizable suffering is ADHD diagnosed.

ADHD, as a neurobiological disorder, has largely genetic causes. However, it can have very different consequences depending on the individual, as environmental factors also influence the individual course. In most cases, individuals with ADHD and their relatives are under considerable pressure: failures at school or work, drug use, and the development of other mental disorders have often been observed. In addition, there is a significantly increased risk of suicide, accidents, and unintentional injuries. 

However, these general risks need not be relevant in each case. Therefore, treatment depends on the severity, the level of suffering, the particular symptoms and problems, and the person’s age.

Is ADHD genetic?

Is ADHD hereditary? It tends to run in families, and there is a high risk that twins share the disease. Based on family and twin genetic studies, heritability for the risk of being affected by ADHD as a child is estimated at 70% to 80%.

Is ADHD a genetic disorder? Individual genes have very specific influences on the development of the condition, and none alone can cause such a diverse behavioral abnormality as observed in the disorder. At least 14 to 15 genes are thought to be important in its development. 

So, can ADHD be genetic and influence a predisposition? Not entirely. The genetic peculiarities influence the neurophysiology and chemistry in specific control circuits of the brain. Even if this does not initially show any outward changes, there may be a basic predisposition that can nevertheless lead to disorders such as ADHD later on due to further environmental factors. 

Genes of the dopaminergic and serotonergic systems, including DRD4, SLC6A3 (DAT1), and DBH, are thought to be associated with the risk of developing ADHD. The particular genetic abnormalities associated with ADHD do not cause the disorder by themselves. In combination with specific variants in other genes, they can also trigger other related or unrelated conditions.

Current Research on ADHD (Updated May 2021)

The discovery of the first genome-wide significant risk loci for attention-deficit/hyperactivity disorder was published in 2018 on a paper that explored the highly heritable behavioral disorder. This work and this other study on the genetics of attention deficit hyperactivity disorder provide an affirmative answer to the question, “Is ADHD inherited?”

After decades of genetic research, there is extensive data on which genetic variants cause a predisposition. In this study, researchers use mediation analyses to explain the relationship between polygenic risk for ADHD and its core symptoms.  A couple of years before that, Nature published this article on the relationship between ADHD and genetics. 

There are many studies for the treatment of the condition for children as it seems to have a more significant sociological impact. This research, however, focuses on cognitive-behavioral interventions for attention deficit hyperactivity disorder in adults. This interesting study about the relationship between creativity and ADHD focuses on the positive side of having the condition. 

On that same line of positivity, this 2020 paper discusses the positive aspects of attention-deficit/hyperactivity disorder among famous people

Since we want to point out the relationship between ADHD and genetics, this 2020 article on the recent advances in understanding of attention deficit hyperactivity disorder makes in-depth research on it. 
More recent research unveils the treatment production for adults with ADHD during the COVID-19 pandemic.

Epidemiology (Part 4 of Is ADHD genetic?)

According to a national 2016 parent survey from the Centers for Disease Control and Prevention (CDC), 6.1 million (9.4%) of children were diagnosed with the learning disability of ADHD sometime in their life. This includes:

  • 388,000 children between 2-5 years
  • 2.4 million children between 6-11 years
  • 3.3 million children between 12-17 years

About 5 in 10 children with ADHD also had behavior or conduct problems, and about 3 in 10 had anxiety

Boys are more likely to be diagnosed than girls (12.9% vs. 5.6%), and females are more likely to have problems primarily with inattention. 

Based on a map created in 2007, there is a higher prevalence of the disorder in the southeast part of the United States, with a relatively low majority in the southwest. Darker blue represents about 10-16% of Youth 4-17 who have ever been diagnosed with ADHD, while lighter blue represents about 5-10% who have ever had the disorder.

Prevalence of ADHD in the United States
Prevalence in the United States in 2007. Wikipedia. CC-Attribution-Share Alike 3.0 Unported.

A 2020 data brief from the National Center for Health Statistics revealed that black children between the ages 3 and 17 are more likely to be diagnosed than white and Hispanic children. Interestingly, the same data shows that children with parents having a higher degree of education are less likely to be diagnosed.

Symptoms (Part 5 of Is ADHD genetic?)

Three main characteristics define ADHD: Inattention, hyperactivity, and impulsivity. It is normal for a child with ADHD to exhibit some of these factors. In children, these behaviors are more severe, occur more often, and interfere with daily life. 

Healthline identifies 14 childhood signs of ADHD including:

  1. Self-focused behavior
  2. Interrupting
  3. Problems with patience
  4. Emotional turmoil
  5. Fidgeting
  6. Problems playing quietly
  7. Unfinished tasks
  8. Lack of focus
  9. Avoidance of tasks
  10. Mistakes
  11. Daydreaming or becoming easily distracted
  12. Trouble getting organized
  13. Forgetfulness
  14. Symptoms in multiple settings

Although symptoms start in childhood and are often diagnosed then, the disorder continues into adulthood, and sometimes a diagnosis is not made until that time. Symptoms usually lessen with age, but they may still interfere with daily life. In adults with attention deficit hyperactivity disorder, the main features of ADHD may include difficulty paying attention, impulsiveness, and restlessness. Symptoms can range from mild to severe.

Approximately 75% of people living with ADHD have another mental disorder, and 60% have multiple concomitant mental disorders. Depression is at least five times more common in adolescents with ADHD than in adolescents without. When depression as a concomitant disorder does not begin until several years after the onset of ADHD, it is assumed to be at least partly a consequence of the particular stresses of ADHD. Anxiety disorders, sleep disorders, and obsessive-compulsive disorder are also common diseases that often occur at the same time as ADHD.

Causes (Part 6 of Is ADHD genetic?)

Is ADHD genetic or environmental? Both environmental and genetic factors play a role in the onset.

Neurobiology

People with ADHD have apparent differences compared to the general population in various areas of their brains and brain-associated cells. Some of these differences include the volume and function of the brain itself, pathways of nerve fibers on neurons, and transmission of signals.

Area of the brain affected
Reduced brain volume on the left side has been observed in ADHD. Wikipedia. CC-Attribution-Share Alike 4.0 International.

Pollutants

In particular, two pollutants, lead and PCB, have been associated with an increased risk of ADHD. There is a statistical association between exposure to the heavy metal lead and the occurrence of ADHD, but no causal relationship has yet been proven. Polychlorinated biphenyls (PCBs), are now banned worldwide but are still prevalent almost everywhere as contaminants.

Other factors

Pregnancy and birth complications associated with brain development, lowered birth weight, infections, exposure to environmental toxins, central nervous system disease, and brain injury also contribute to ADHD – so are exposures to smoking, drugs, and alcohol that occur during pregnancy. Many of these factors are also genetic! 

Diagnosis (Part 7 of Is ADHD genetic?)

There is no specific test to diagnose ADHD. This complicates the diagnosis procedure since symptoms and traits of the disorder are distributed at various levels across all populations. It is only when the symptoms are classified as severe enough that a diagnosis can be made. 

Medical specialists or psychologists can only make a proper and valid ADHD diagnosis with sufficient specialized knowledge. They usually follow guidelines set forth by the Diagnostic and Statistical Manual of Mental Disorders (DSM) from the American Psychiatric Association (APA). This resource is available to the public for informational purposes only and should not be used to self-diagnose or diagnose a child. 

Six or more inattention symptoms and six or more symptoms of hyperactivity and impulsivity for children up to age 16 years, or five or more for adolescents age 17 years and older and adults are required for diagnosis. Symptoms of inattention must be present for at least 6 months, and they are inappropriate for developmental level. 

Other conditions must also be met:

  • Several inattentive or hyperactive-impulsive symptoms were present before age 12 years.
  • Several symptoms are present in two or more settings (such as at home, school, or work; with friends or relatives; in other activities).
  • There is clear evidence that the symptoms interfere with or reduce the quality of social, school, or work functioning.
  • The symptoms are not better explained by another mental disorder (such as a mood disorder, anxiety disorder, dissociative disorder, or a personality disorder). The symptoms do not happen only during the course of schizophrenia or another psychotic disorder.

Based on the condition, one of three kinds of ADHD may be diagnosed:

  • Combined Presentation: if enough symptoms of both criteria inattention and hyperactivity-impulsivity were present for the past 6 months
  • Predominantly Inattentive Presentation: if enough symptoms of inattention, but not hyperactivity-impulsivity, were present for the past six months
  • Predominantly Hyperactive-Impulsive Presentation: if enough symptoms of hyperactivity-impulsivity, but not inattention, were present for the past six months.

If symptoms change, the category may also change.

Prevalence of disorder subtypes

Prevalence of ADHD subtypes. Wikipedia. CC-Attribution-Share Alike 4.0 International.

Treatment (Part 8 of Is ADHD genetic?)

There are several treatments, and the particular treatment used will depend on the severity of the case and the individual patient’s needs, especially if the patient is a child. 

Types of treatment include:

  • Psychotherapy
  • Medications

Psychotherapy and Psychosocial Interventions

If younger than six years, the American Academy of Pediatrics (AAP) recommends parent training in behavior management as the first line of treatment before trying medication. Children younger than 6 tend to have more side effects from the medication, and there is less research on the long-term effects in children who started taking ADHD medication very young. 

For children six years of age and older, the recommendations include medication and behavior therapy together. In addition to parent training, it is also recommended that students engage with peer interventions that focus on behavior; and organizational skills training. AAP recommendations also include adding behavioral classroom intervention and school supports for both parents and teachers.

The National Institute of Mental Health (a part of the National Institutes of Health) also lists several other types of therapies that may help families navigate the illness and improve outcomes. These therapies include:

  • Behavioral therapy helps a patient change behavior. This often involves positive and negative reinforcement as well as social skill training. It also allows individuals to control impulsive behaviors. 
  • Cognitive-behavioral therapy also teaches a person mindfulness techniques or meditation. Therapists also help ADHD patients with thinking before acting or resisting the urge to take unnecessary risks.
  • Family and marital therapy helps families handle disruptive behaviors, encourage changes, and improve interactions.
  • Stress management techniques can benefit parents of ADHD patients.

Support groups allow affected families to connect and share problems and concerns.

Medications

Medication can help children manage their symptoms in their everyday lives and help them control the behaviors that cause difficulties with family, friends, and school.

Several different types of medications are FDA-approved to treat ADHD in children as young as six years:

Stimulants are the best-known and most widely used ADHD medications. Stimulants work by increasing the brain chemicals dopamine and norepinephrine, which are essential for thinking and attention. Between 70-80% of children with ADHD have fewer symptoms when taking these fast-acting medications. Some side effects include decreased appetite, sleep problems, tic, personality changes, increased anxiety and irritability, stomachaches, and headaches. 

Non Stimulants were approved for the treatment of ADHD in 2003. They do not work as quickly as stimulants, but their effect can last up to 24 hours. They are often prescribed for patients with severe side effects from stimulants or for who stimulants were not effective. 

Antidepressants can also be helpful for those who do not respond well to stimulants and are often prescribed at the same time as other medications, especially if a patient also suffers from another condition such as anxiety or depression.  

Each child will react to medications differently. It’s essential to work with healthcare providers and follow medical advice to find a regiment that best fits the patient. Healthcare providers often adjust the dose of medication to find the right balance between benefits and side effects. 

Treatment for children and adults with attention deficit hyperactivity disorder is similar. Adult ADHD treatment includes medications, counseling, and therapy for any mental health conditions that occur along with ADHD.

If you liked this article, you should check out our other posts in the Nebula Research Library!