ADHD is defined by its symptoms (rather than its cause)

The DSM-V (the guide that lays out the criteria to be used by doctors, mental health professionals, and other qualified clinicians when making a diagnosis of ADHD) lists ADHD in the category of ‘Neuro-developmental Disorders’ and defines it as:

“a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with development, has symptoms presenting in two or more settings (e.g. at home, school, or work), and negatively impacts directly on social, academic or occupational functioning”

If you look at Getting a Diagnosis you will notice there is a checklist of symptoms from which children must have at least six symptoms from either, or both categories, while older adolescents and adults (over age 17 years) must present with five.

Care must be taken to rule out other conditions that may mimic ADHD

Symptoms of hyperactivity, distractibility, impulsivity, inattention and so on may be all too real but, before attributing them to ADHD and treating as ADHD accordingly, it would be wise to explore some other conditions that may result in ADHD symptoms.

This is a difficult task because many ADHD diagnoses are often accompanied by a co-morbid condition diagnosis such as anxiety.


  • Asperger’s Syndrome
  • Attachment Disorders/Reactive Attachment Disorder (RAD)
  • Autism Spectrum Disorder
  • Biochemical imbalances
  • Borderline Personality Disorder
  • Disruptive Mood Dysregulation Disorder (DMDD)
  • Dyslexia
  • Executive Function Difficulties
  • Fetal Alcohol Syndrome
  • Food intolerances & Sensitivities
  • Fragile X Syndrome
  • Giftedness
  • Hearing problems - including Auditory Processing Disorder
  • Medical conditions e.g. thyroid disorder
  • Mood disorders (e.g. Anxiety, Depression, Bipolar Disorder)
  • Non-Verbal Learning Disabilities (NVLD)
  • Obsessive Compulsive Disorder (OCD)
  • Post-Traumatic Stress Disorder (PTSD)
  • Schizophrenia
  • Seizure disorders
  • Sensory Processing Disorder
  • Sleep Disorders
  • Specific Learning Difficulties
  • Speech & Language Disabilities
  • Substance Abuse
  • Traumatic Brain Injury
  • Vision problems

If these conditions are diagnosed and treated it may be that the symptoms associated with ADHD may disappear as a result.

Receiving the correct treatment for the correct diagnosis, as early as possible, is vital as misdiagnosis can result in a delay or lack of appropriate treatment with significant impact on an individual.

See below for more detail on these conditions.

The conditions that are also co-morbid are covered here.
Some examples of this include having high copper levels which lead to hyper-excitablity of the nervous system and can affect neural activity and so play a key role in symptoms of focus and attention.

On the other hand, low zinc decreases regulation of GABA (Gamma Amino Butyric Acid) – a calming neurotransmitter.

Proper copper/zinc balance can alleviate symptoms of inattention and lack of focus.

Yeast toxicity is another issue that can also lead to poor focus, inattention, impulsivity and anxiety.
Foetal Alcohol Spectrum Disorder (FASD) refers to a range of problems caused by a mother exposing an unborn baby to alcohol during pregnancy, which harm the development of the foetal nervous system, including the brain. This results in the child having learning and behavioural problems, which may include:

  • Learning difficulties
  • Memory problems
  • Impulsiveness
  • Limited attention span / ease of distraction / hyperactivity
  • Difficulty relating actions to consequences
  • Difficulty following instructions (but able to repeat them verbally)
  • Difficulty with abstract thinking – e.g. mathematics, money or time
  • Slow cognitive processing (thinking)
  • Difficulty with social relationships

However, children with FASD also have unique facial features which include:

  • Short horizontal length of the eye opening, from the inner corner to the outer corner of the eye
  • A smooth philtrum (the ridged area of skin between upper lip and nose)
  • A thin upper lip
Food sensitivity or intolerance can be seen when a particular food causes some type of physical or behavioural symptom.

Food sensitivities/intolerances can cause increased hyperactivity, impulsivity and lack of concentration.

A 2011 study published in the Lancet looking at diet’s effect on ADHD symptoms showed that 64% of the children on a restricted diet had significant improvement in their ADHD symptoms while none of the control group had improved.

Other studies have shown similar results so eliminating certain foods can help some children’s ADHD symptoms.
Fragile X Syndrome is a genetic condition causing intellectual disability, behavioural and learning challenges and various physical characteristics.

It is also the most common single gene cause of autism worldwide.

It appears in people of all ethnic, racial and socio-economic backgrounds.

Though Fragile X syndrome occurs in both genders, males are generally affected with greater severity.

It is estimated that 5 per cent of people with a diagnosis of an Autism Spectrum disorder also have Fragile X syndrome.
Sometimes gifted children may show behaviours that mimic ADHD. For example, they may appear hyperactive because they ask so many questions and are so excited about learning.

Alternatively, they may not wish to take part in age-expected activities because they wish instead to focus on an area of interest.

Boredom with work that is below their intellectual level can lead to inattention as well as feelings of depression.

In such cases, the child does not have ADHD and the appropriate intervention is to provide more challenging tasks so as not to risk academic and social failure despite superior potential.

However, it is possible to have both ADHD and giftedness. This combination is often described as 2E (Twice Exceptional)
Hearing problems are another common problem in children, which can cause symptoms of attention problems. If a child cannot hear their parent, teacher or other children they are going to appear inattentive and unfocussed or carry out tasks incorrectly. As with vision problems, hearing difficulties can often go undiagnosed as the child, or indeed adult, may not realise they are not hearing at the same level as other people. Hearing problems can be the result of many different causes some of which are listed below:

  • Excessive ear-wax causing a blockage;
  • Ear infections and sometimes resulting debris left blocking the ear;
  • Tinnitus - high pitched ringing, buzzing or other sounds in the ear;
  • Auditory Processing Difficulties;
  • Injuries to the ear such as a ruptured ear drum;
  •  Side effect of some medications;
  • Underdevelopment of the inner ear or auditory nerve;
  • Congenital diseases e.g. Usher syndrome;
  • Non-congenital diseases e.g. illnesses causing high fevers;
  • Ear-based tumours;
  • Heredity.

Visit your GP in the first instance for them to check the ears. They may then refer you on to an Ear Nose & Throat specialist or audiologist for further investigations.
Symptoms of ADHD and a thyroid disorder can appear very similar.

An article in Clinical Endocrinology stated, “Despite being within the normal range, high TSH concentrations are associated with a lower cognitive function, and high TSH and low free T4 with ADHD symptoms”.

The study revealed when TSH records are at the top of the normal range, there is a correlation with the same learning disorders of those who have ADHD.
Current research suggests that symptoms of psychiatric conditions such as OCD, paranoia, tics, anxiety, behavioural issues and/or new learning difficulties have been associated with PANDAS - at least in some cases.

PANDAS results from the effect of the body's own immune system's antibodies attacking parts of the brain.

PANDAS is a little known illness resulting in the sudden onset of mental health issues.

PANDAS is an acronym for a condition called Paediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus (PANDAS).

The onset of PANDAS usually occurs following an ear, nose or throat (ENT) infection from Group A Beta Haemolytic Streptococcus (GABHS). GABHS antibodies in some cases can damage parts of the brain resulting in a range of behavioural disorders such as OCD, Oppositional Defiant Disorder, Tourette’s, ADHD and even psychosis.
Because of their impulsivity and inattention, ADHD children are at high risk of physical injury.

Brain injury can either aggravate ADHD’s symptoms or produce a syndrome named Secondary-ADHD (S-ADHD).

As a matter of fact, 20% of children with brain injury develop ADHD and the more severe the head trauma, the higher the risk.
Vision problems are usually extremely easy to correct once the problem is diagnosed but can often be overlooked.

Vision-related problems are often hard to pick up in children, especially younger children, as the child may not recognise or wish to admit the problem. They may assume that everybody has the same view of the world as they do, so not think to mention it.

However, if they are struggling to see, this may well result in a child having attention problems.

There are various vision problems that can occur:

  • Myopia - short-sightedness
  • Hyperopia - long-sightedness
  • Astigmatism - a misshapen cornea or lens causing blurring of vision
  • Presbyopia - problems focussing on nearby items
  • Binocular vision problems - eyes not working in tandem properly
  • Eye fatigue - fatigue of the eye muscles due to prolonged computer use
  • Lazy eye - when brain receives conflicting visual information from both eyes it may switch off the vision in one eye to obtain a clearer picture
  • Colour blindness - inability to see particular colours

Most common vision problems can be easily diagnosed by a qualified ophthalmologist via a simple vision test.

Some vision problem may require more specialised testing and treatment via a behavioural optometrist.

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