What is ADHD?

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental condition, affecting 5% of the population.

ADHD is something that exists from birth but might not be diagnosed until people are older. There are three core symptoms of the condition including poor attention, hyperactivity, and impulsive behaviors, however how they present and affect people can vary. Hyperactivity and impulsivity usually occur together, however one may occur without the other.

Symptoms must have existed for at least six months, be inappropriate for the individual’s developmental level, and negatively impact their social and academic/occupational activities.

What are the symptoms of ADHD?


  • Often fails in paying attention to details or makes careless mistakes in schoolwork, at work, or with other activities
  • Often has trouble holding attention on tasks or play activities
  • Often does not seem to listen when spoken to directly
  • Often does not follow through on instructions and fails to finish schoolwork, chores, or duties in the workplace (e.g., loses focus, side-tracked)
  • Often has trouble organizing tasks and activities
  • Often avoids, dislikes, or is reluctant to do tasks that require mental effort over a long period of time (such as schoolwork or homework)
  • Often loses things necessary for tasks and activities (e.g. school materials, pencils, books, tools, wallets, keys, paperwork, eyeglasses, mobile telephones)
  • Is often easily distracted
  • Is often forgetful in daily activities

Hyperactive and impulse behaviour

  • Often fidgets with or taps hands or feet, or squirms in seat.
  • Often leaves seat in situations when remaining seated is expected.
  • Often runs about or climbs in situations where it is not appropriate (adolescents or adults may be limited to feeling restless).
  • Often unable to play or take part in leisure activities quietly.
  • Is often “on the go” acting as if “driven by a motor”.
  • Often talks excessively.
  • Often blurts out an answer before a question has been completed.
  • Often has trouble waiting his/her turn.
  • Often interrupts or intrudes on others (e.g., butts into conversations or games)

Additional criteria

  • 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 across other activities)
  • The symptoms are not explained by another mental condition 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

Subtypes of ADHD

Based on the different types of ADHD symptoms, three ADHD subtypes can be diagnosed:

  • Predominantly inattentive: if enough symptoms of inattention, but not hyperactivity-impulsivity, were present for the past six months
  • Predominantly hyperactive-impulsive: if enough symptoms of hyperactivity-impulsivity, but not inattention, were present for the past six months
  • Combined: if enough symptoms of both inattention and hyperactivity-impulsivity were present for the past six months

Gender differences in ADHD

There is a lot of research which highlights the gender differences in ADHD. Men are more likely to experience higher levels of hyperactivity and impulsivity whereas women are more likely to show higher levels of inattention. Clinicians have been reported to prescribe less medication to women than men, which is likely because more men are diagnosed with ADHD because of their symptoms being more obvious.

Adding objective ADHD tests to the evaluation process can help mitigate gender bias in diagnoses by comparing the three core symptoms to a gender control group. This is incredibly useful for symptoms that are harder to measure, like inattention.

ADHD and comorbidity

Many neurodevelopmental conditions are comorbid with others. 80% of people with ADHD have at least one other psychiatric disorder, which may include:

  • Autism spectrum disorder
  • Anxiety
  • Depression
  • Obsessive compulsive disorder (OCD)
  • Oppositional defiant disorder (ODD)
  • Personality disorders
  • Substance use disorder
  • Learning disabilities

Gender differences and comorbidities emphasize the need for accurate, data-driven clinical evaluations and diagnoses.

ADHD diagnosis

A diagnosis of ADHD should only be made by a clinical psychologist, psychiatrist, pediatrician or other appropriately qualified healthcare professional. A full clinical evaluation should include both subjective and objective evaluations:

  • Physical examination
  • Clinical interviews
  • Rating scales
  • A continuous performance task like QbTest or QbCheck to gather data on the three core symptoms

When ADHD symptoms meet the criteria of the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5)*, the individual can be diagnosed with it and next steps can be discusseed around managing symptoms.


*Please note: In Europe, the International Classification of Mental and Behavioural Disorders 10th revision (ICD-10) may be used as medical classification system, which includes different diagnostic terminology and criteria to the DSM-5.