In recent years, ADHD awareness has surged, leading to a notable rise in both diagnoses and treatment. With an abundance of ADHD-related content available online, it’s important to recognise that ADHD isn’t a one-size-fits-all condition. In this article, we delve into the three distinct types of ADHD and explore their diagnostic criteria. The aim is to help people clarify and explain how ADHD is identified. This is not a diagnostic tool and will not tell you if you have ADHD or not.

What is ADHD?

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental difference characterised by persistent patterns of inattention, hyperactivity, and impulsivity (DSM-5, 2013). These symptoms can significantly impair daily functioning and often become evident in early childhood. Contrary to what its name suggests, ADHD isn’t about a lack of attention; rather, it reflects differences in how the brain regulates attention.

Central to ADHD is an atypical balance of chemicals in the prefrontal cortex, the area of the brain responsible for executive functioning.

Executive functions are the mental processes that allow us to plan, focus, remember, and manage tasks. They include:

1. Working memory – holding and manipulating information for short-term use.
2. Self-monitoring – observing and evaluating one’s thoughts, behaviours, and actions.
3. Inhibition/impulse control – the ability to resist impulsive urges and refrain from inappropriate or disruptive behaviours.
4. Emotional regulation – the ability to recognise, understand, and effectively manage one’s emotions and reactions.
5. Flexibility – adapting and adjusting to changing circumstances, perspectives, or demands.
6. Planning and prioritisation – creating a systematic approach to achieving goals, including breaking tasks into steps.
7. Task initiation – the ability to independently begin a task or activity without procrastination.
8. Organisation – structuring and arranging information, materials, or physical spaces.

Understanding these functions helps us grasp how ADHD affects thinking and behaviour. Research suggests that individuals with ADHD experience about a 30% delay in the development of their executive functions, and adults with ADHD typically develop only approximately 75-80% of the capability of their peers.

What Are the Subtypes of ADHD?

ADHD is diagnosed based on criteria outlined in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th Edition). The DSM-5 recognises three subtypes:

• Inattentive Type (ADHD-I): Individuals primarily struggle with sustained attention and organisation. They may experience difficulty focusing and completing activities. This subtype is often characterised by a tendency to daydream.
• Hyperactive-Impulsive Type (ADHD-H): Marked by physical restlessness and impulsivity. Hyperactivity can also be internalised and experienced as internal restlessness, leading to difficulties in environments requiring sustained calm.
• Combined Type (ADHD-C): A combination of both inattentive and hyperactive-impulsive traits. Individuals experience difficulties across all areas, including attention and impulse control.

[Image comparing the three types of ADHD: Inattentive, Hyperactive-Impulsive, and Combined]

How Is ADHD Diagnosed?

The diagnostic process is thorough. For a diagnosis of ADHD-I, six or more traits of inattention must be present for children (up to age 16), or five or more for those aged 17 and over. Symptoms must have persisted for at least six months and include:

• Failing to give close attention to details or making careless mistakes.
• Trouble sustaining attention on tasks.
• Not seeming to listen when spoken to directly.
• Failing to follow through on instructions and failing to finish tasks.
• Trouble organising tasks and activities.
• Avoiding tasks that require sustained mental effort.
• Losing things necessary for tasks.
• Being easily distracted and forgetful in daily activities.

For a diagnosis of ADHD-H, the same numerical threshold applies (six for children, five for adults) regarding symptoms of hyperactivity-impulsivity:

• Fidgeting or squirming in seats.
• Leaving seats in situations where remaining seated is expected.
• Feeling restless or acting as if "driven by a motor."
• Being unable to engage in leisure activities quietly.
• Talking excessively and blurting out answers before questions are finished.
• Having trouble waiting for a turn.
• Interrupting or intruding on others.

For a diagnosis of ADHD-C, criteria for both inattention and hyperactivity-impulsivity must be met. Additionally:

• Symptoms must have been present before age 12.
• Symptoms are present in two or more settings (e.g., home and work).
• There is clear evidence that symptoms reduce the quality of social, academic, or occupational functioning.
• Symptoms are not better explained by another mental health condition.

Reflective Questions

1. Which ADHD subtype resonates most with your own experiences, or with someone you know?
2. How might understanding these subtypes influence your approach to managing symptoms?
3. In what ways could improved executive functioning skills help in daily life, regardless of a diagnosis?

Understanding ADHD subtypes allows us to appreciate the diversity within the diagnosis. By learning these nuances, we can better support those living with ADHD in leading their healthiest and happiest lives.

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