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

focus adhd

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

Additional Information

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

Attention-deficit/hyperactivity disorder (ADHD) is a 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 pure 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 an 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 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 the individual course is also influenced by environmental factors. 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 individual case. Therefore, treatment depends on the severity, the level of suffering, the particular symptoms and problems, and the age of the person affected.

Epidemiology (Part 2 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 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 children with ADHD had anxiety. 

Boys are more likely to be diagnosed with ADHD than girls (12.9% vs 5.6%), and females with ADHD 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 prevalence in the southwest. Darker blue represents about 10-16% of Youth 4-17 have ever diagnosed with ADHD while lighter blue represents about 5-10% have ever had the disorder. 

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

Symptoms (Part 3 of Is ADHD genetic?)

ADHD is defined by 3 main characteristics: Inattention, hyperactivity, and impulsivity. It is normal for children to exhibit some of these factors. In children with ADHD these behaviors are more severe, occur more often, and interfere with daily life. 

Healthline identifies 14 signs of ADHD in children:

  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 often 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 ADHD sufferers 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 ADHD. 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 4 of Is ADHD genetic?)

Both environmental and genetic factors play a role in the onset of ADHD.

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, the pathways of nerve fibers on neurons, and the 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

Two pollutants in particular, 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 are also considered risk factors – so are exposures to smoking, drugs, and alcohol that occur during pregnancy. Many of these factors are also genetic!

Is ADHD genetic?

ADHD 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%.

Individual genes have very specific influences on the development of ADHD 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. 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 as a result of further environmental factors. 

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

Diagnosis (Part 5 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. 

A useful and valid ADHD diagnosis can only be made by medical specialists or psychologists 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 made available to the public for informational purposes only and should not be used to self-diagnosis or diagnose a child. 

Six or more symptoms of inattention as well as 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 is 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 6 of Is ADHD genetic?)

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

Types of treatment include:

  • Psychotherapy
  • Medications

Psychotherapy and Psychosocial Interventions

If younger than 6 years, the American Academy of Pediatrics (AAP) recommends parent training in behavior management as the first line of treatment, before medication is tried. 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 6 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 helps individuals in controlling impulsive behaviors. 
  • Cognitive behavioral therapy also teaches a person mindfulness techniques, or meditation. Therapists also help patients with skills such as 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 ADHD symptoms in their everyday life and can help them control the behaviors that cause difficulties with family, friends, and at school.

Several different types of medications are FDA-approved to treat ADHD in children as young as 6 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 ADHD 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 who have severe side effects from stimulants or for who stimulants were not effective. 

Antidepressants can also be useful 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 important 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 adult ADHD is similar to treatment for childhood ADHD. Adult ADHD treatment includes medications, counseling, and treatment 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!