Written by Brittni Bresee on:

Medically Reviewed by our Medical Affairs Team

Few mental disorders generate as much controversy and debate as attention-deficit/hyperactivity disorder.

ADHD is one of the most common disorders found in children and adults today. Despite its frequency, there is still a significant argument about the exact cause.

Studies have shown no single factor determines the exact etiology of the disorder. It involves a complex interaction of biological and environmental factors. (Wolraich, 2000).

Evolution of ADHD Understanding

In the last century it ADHD symptoms w to Minimal Brain Dysfunction, or MBD, as a result of trauma to the brain. Further studies failed to support these claims the MBD claims.

Several years later, attention-deficit/hyperactivity disorder looked to be a hyperkinetic reaction of childhood. But the symptoms between children varied too for this idea to solidify.

Some children were hyperactive and impulsive. In contrast, other children were less hyperactive but still had difficulty paying attention.

ADD (Attention Deficit Disorder) was then introduced with two subtypes. To address both sets of symptoms, they gave the disorder two subtypes. ADD with hyperactivity and ADD without hyperactivity.

Further understandings combined these into one disorder;

ADHD (Attention-deficit/hyperactivity disorder) with two subcategories: the inattentive and the hyperactive/impulsive.¹

The Biology of ADHD

The possible neurobiological basis of attention-deficit/hyperactivity disorder depends on :

  • Brain structures
  • Gene transmission
  • Chemical messengers of the nervous system
  • Cognitive processing

Brain structures

A craft illustration for adhd mind.

There have been two types of imaging that have advanced the ADHD diagnosis.

One is Functional Magnetic Resonance Imaging (FMRI), and Single-Photon Computerized Tomography (SPECT) scans.

With these tests, it becomes possible to study the brain in more detail.

Brain scans of the attention-deficit/hyperactivity disorder subjects shed a whole new light on the matter. This quite telling information showed scientists different brain structures. Different brain structures can mean many different things.

A person with ADHD/ADD shows to have less activity in the frontal region of the brain. Meanwhile, having more activity in the cingulate gyrus region of the brain.

The frontal region of the brain handles executive functioning. And the cingulate gyrus area handles focusing, attention, and response selection. (Linda Wilmshurst 2015 )

Different brain structures show that children with attention-deficit/hyperactivity disorder have different brain matter ratios.

They denote a 5% reduction in total brain volume and a 12% reduction in brain volume of the prefrontal cortex (PFC)⁸. It is crucial for complex and planned behavior and overcoming goals.

It is not hard to understand why these children a lot of times have trouble in school. The main point of a school-aged child is to learn skills needed for efficiency and comprehension.

Children who are inattentive have a “slow” information processing style. They also display problems with focus or have selective attention.

Lack of attention to detail often results from an information overload.  Academic difficulties include the ability to complete homework while maintaining interest. This can appear to be a lack of motivation. Yet this could be a sign of hyperactivity and/or impulsivity.

Hyperactivity symptoms can include:

  • irritable or fickle behavior
  • Sitting problems
  • excessive movement
  • Problems engaging in quiet play
  • Always on the move
  • Continuous speech

For a more detailed list of hyperactivity, click here

Impulsivity symptoms may include:

  • Blurs answers and comments
  • Impatient, has problems taking turns
  • Interfering with others

Three areas of executive functioning that can be problematic for people with ADHD :

  • Working memory. This is the ability to keep helpful information available when needed. This helps us with planning, reading comprehension, reasoning, and problem-solving skills.
  • Sense of time. Studies have linked low levels of dopamine to a poor perception of time. This may be responsible for poor time management skills in individuals with attention-deficit/hyperactivity disorder.
  • Constant concentration. The prefrontal cortex sends signals to the brain that tune out environmental stimuli. When the PFC is not receiving proper communication, it is unable to do this. This results in a lack of constant concentration needed for doing certain tasks.

Individuals with a more regulated frontal region perform executive functions much easier. They often express these qualities;

  • Flexibility
  • Shift focus between tasks when needed
  • Adapt strategies as needed
  • Successful problem-solving skills
  • Retaining information
  • Completing problem-solving tasks
  • The overall use of the working memory

Gene Transmission

A phenotype is the observation of the genes’ ability to interact with the environment. Epigenetics is the study of how cells control gene activity. These areas of study have proven experience can alter gene structure and function. This occurs through modification of gene expression.

Different expressions may not depend on DNA structure but the regulatory markers. The markers control how and when a gene passes.

This indicates that certain environmental hazards will not affect everyone the same way.

Some are “immune” to the effect. In comparison, others will be susceptible to developing  ADHD in the presence of the hazard.

For example:

  • The rate that our body is able to remove toxins depends on genetic predisposition.
  • The levels of lead in the blood vary by how an individual absorbs iron. For decades it scientists have been aware that lead is a neurotoxic substance. It can cause hyperactivity and other health problems.
  • The gene characteristics of a person can change nutritional additives. In some individuals, this modification process doesn’t work.
  • Low birth weight (<2500g) is a specific risk factor for inattention/hyperactivity.
  • Alcohol exposure increases the offspring’s risk of attention-deficit/hyperactivity disorder. Although, these children may have a somewhat distinct neuropsychiatric condition.
  • Possible population studies state the presence of household and outdoor insecticides.

Chemical Messengers of the Nervous System

Neurotransmitters are a type of messenger we have to send chemicals for communication. They travel through the body, constantly making connections needed for every moment.

The Role of Treatment Research found low levels of certain neurotransmitters; Dopamine, norepinephrine, epinephrine in children with ADHD.  These particular neurotransmitters are responsible for attention and motor activity.

A popular medication prescribed for attention-deficit/hyperactivity disorder is,  Adderall. This medication increases the number of neurotransmitters in the brain’s neural processing. This is how it can help improve the symptoms of ADHD. (Barkley, 1998). It also has a long list of side effects, but to some, their need outweighs the warnings on the label.

Approximately 50% of children with attention-deficit/hyperactivity disorder have a parent who also has the disorder. (Biederman et al., 1995) Studies suggest that up to 75% of the etiology is connected to genetic factors. (Sherman, Iacono, & McGue, 1997). Doctors have known that ADHD risk increases two- to four-fold among first-degree relatives.

One research approach indicated that six genes had common markers:

  • Dopamine transporter (DAT1),
  • Dopamine D4  (DRD4)
  • Dopamine  D5 Receptors  (DRD5)
  • Serotonin Transporter (5HTTPLR)
  • HTR1B
  • SNAP25

Signs of ADHD

A notebook list of factors determining what adhd can look like.

  • Infant period (1month–1year) :

Although it is difficult to diagnose attention-deficit/hyperactivity disorder before the age of 3 years, children who have short tempers at this early age have been more likely to develop ADHD.  Calming these children is more difficult than with their peers without attention-deficit/hyperactivity disorder. Other early signs include excessive activity, poor sleep patterns, and nervous parents.

  • The toddler period (1–2.5 years) :

Between the age of 1 – 2.5 years old, toddlers with ADHD show symptoms of lack of self-control and higher levels of disorganization.

  • The preschool  period  (3–6 years)

In the preschool period  (3–6 years), the lack of self-control persisted. At the same time, non-ADHD peers show increased maturity and increased self-control. Parents describe children with attention-deficit/hyperactivity disorder as more demanding, stressful, and problematic.

  • The School-Age Child (6-11 Years)

Between 6-11 years, children often struggle when faced with academic and social demands. The children who are hyper and impulsive with ADHD struggle with these demands. The nature of their academic concerns is more related to the tendency to rush through tasks. Doing this, they sacrifice accuracy for speed.

These children have little tolerance for frustration and also tend to give up when they do not have an immediate solution.

This impulsive behavior also puts these children at greater risk of accidental injury. Throughout their adolescence, at least half of these will continue to show symptoms.

  • Adolescents with attention-deficit/hyperactivity disorder

Adolescents with ADHD are not very equipped to meet everyday challenges. Such as increased workload and independent study skills. Other prevalent social and emotional impacts at this developmental stage include:

  • an increased risk of reckless driving accidents
  • participation in other high-risk behaviors

ADHD and comorbidities⁸ Symptoms of depression and bipolar disorder often overlap with symptoms of attention-deficit/hyperactivity disorder. This makes the diagnosis difficult. Among the main symptoms of depression in children is irritability. Neurotic behaviors often manifest as:

  • Anxiety
  • Agitation
  • Short attention span,
  • Poor concentration
  • impulsive responses that resemble ADHD symptoms.

Bipolar symptoms can include pressured speech (fast speech), distractibility, and hyperactivity. It’s easy to confuse them with the symptoms of attention-deficit/hyperactivity disorder, as up to 70% of children with depression also have ADHD.

In another study, nearly 90% of children and 30% of adolescents having both bipolar disorders and attention-deficit/hyperactivity disorder.  Studies show that up to 50% of children with ADHD will go on to develop a conduct disorder. Hyperactive adolescents with attention-deficit/hyperactivity disorder were significantly more likely to use cigarettes and alcohol than their non-hyperactive peers. (Linda Wilmshurst 2015).

Join The Mental Health Community You've Been Dreaming Of


This discord family is a safe place where we can all (anonymously if we choose) talk about and seek help for what is going on in our heads.

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}
Insert About the Author
>