Conclusions: Most likely, no single ADHD biomarker can be identified. However, the use of a combination of markers may help to reduce heterogeneity and to identify homogeneous subtypes of ADHD.
Genetic Biomarkers. The dopamine transporter gene (DAT1 gene) has been linked to the etiopathogenesis of ADHD with many studies on knockout mice for DAT1 showing deficits in inhibitory behavior and hyperactivity. The same gene has also been mapped near a susceptibility locus for ADHD, i.e., 5p13 [47, 48].
Genetics. ADHD tends to run in families and, in most cases, it's thought the genes you inherit from your parents are a significant factor in developing the condition. Research shows that parents and siblings of someone with ADHD are more likely to have ADHD themselves.
Simply put, people with ADHD have areas of the brain that function differently. The disorder begins in childhood, but somewhere between 30 to 70 percent of sons will also be fathers with ADHD. A number of published studies show a clear link to genetics, but it is not 100 percent conclusive.
Genetic screening cannot determine if a person has ADHD. Genetic screening may be helpful to a prescriber in selecting medications to treat ADHD and related conditions. Genetic screening may reveal information about other conditions that will need to be considered.
Heritability in ADHD
According to a recent meta-analysis of twin studies, the heritability of ADHD is estimated at 77–88% [8]. The magnitude is therefore similar to that of autism spectrum disorder (about 80%), bipolar disorder (about 75%), and schizophrenia (about 80%) [6].
Parent and teacher ratings of ADHD symptoms result in high heritability estimates (70–80%) [6].
The Family Connection
There are genetic characteristics that seem to be passed down. If a parent has ADHD, a child has more than a 50% chance of having it. If an older sibling has it, a child has more than a 30% chance.
What is the cause or basis of ADHD? It is an impulse disorder with genetic components that results from imbalances of neurotransmitters.
Twin studies have demonstrated that ADHD in children and adolescents are predominantly under genetic influences (approximately 70–80%), with the remaining variance explained by child-specific environmental experiences (experiences not shared between siblings that make them different from each other) [16, 17].
ADHD has been a subject of great controversy and debate. A number of people who have been diagnosed with the syndrome—some of them psychologists and psychiatrists—have challenged the notion that personality traits such as inattentiveness, impulsivity, and distractibility deserve the label symptoms.
The exposure to stressful life events, and—more specifically—Childhood Trauma, has been shown to predict ADHD onset as well as persistence of the disorder into adulthood (Biederman et al. 1995; Friedrichs et al.
Computerized continuous performance tests (CPT) considered the "gold standard" for diagnosis of Attention Deficit/Hyperactivity Disorder (ADHD) and are widely used. This type of tests measures the number of correctly detected stimuli as well as response time.
Available evidence suggests that ADHD is genetic—passed down from parent to child. ADHD seems to run in at least some families. At least one-third of all fathers who had ADHD in their youth have children with the condition. What's more, the majority of identical twins share the ADHD trait.
Attention deficit hyperactivity disorder (ADHD), one of the most prevalent childhood disorders today, is generally more likely to be diagnosed and treated in boys than in girls.
As you know, one trademark of ADHD is low levels of the neurotransmitter dopamine — a chemical released by nerve cells into the brain. Due to this lack of dopamine, people with ADHD are "chemically wired" to seek more, says John Ratey, M.D., professor of psychiatry at Harvard Medical School in Boston.
A well-balanced diet, exercise, and meditation are all good options for individuals looking to reduce their ADHD symptoms. However, while these natural ADHD remedies may reduce the severity of certain ADHD symptoms, they do not address the individual's underlying brain dysregulation.
ADHD was the first disorder found to be the result of a deficiency of a specific neurotransmitter — in this case, norepinephrine — and the first disorder found to respond to medications to correct this underlying deficiency. Like all neurotransmitters, norepinephrine is synthesized within the brain.
Accidents are the most common cause of death in people with ADHD, and the relative risk of dying is much higher for women than men with ADHD and individuals diagnosed in adulthood. The study is the first to shed light on the role of ADHD in premature death.
ADHD in children was assessed using parent and teacher ratings, while parents completed self-reports. Children were assessed with neuropsychological paradigms measuring IQ, motor, timing, and executive functions. Results: Paternal and maternal ADHD were equally positively related to ADHD in offspring.
In register studies accidents, suicides, and homicides have been the main causes of death in individuals with ADHD [6,7,8]. Cause-specific mortality for suicide was significantly higher for those with ADHD compared to controls in a longitudinal setting [16].
While the exact causes of ADHD have not been identified, genetic studies show there is a strong hereditary component, with an up to a 91 percent likelihood of passing the disorder to your children.
Traumatic stress can worsen ADHD symptoms. Up to 17% of trauma-exposed children meet ADHD criteria, and the co-occurrence of each worsens the effects of the other. Trauma also impacts specific brain regions that may also increase: Inattention, impulsivity, and hyperactivity.