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 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. These 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 to different situations.
5. Flexibility – adapting and adjusting to changing circumstances, perspectives, or demands.
6. Planning and prioritisation – the ability to create a systematic approach to achieving goals, including breaking tasks into steps and determining their relative importance.
7. Task initiation – the ability to independently begin a task or activity without procrastination or hesitation.
8. Organisation – structuring and arranging information, materials, or physical spaces.

Understanding these executive functions helps us grasp how ADHD affects the way a person thinks, feels, and behaves. 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 executive functioning capabilities 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). A diagnosis requires the presence of a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. The DSM-5 recognises three subtypes of ADHD:

• Inattentive Type (ADHD-I): Individuals with this subtype primarily struggle with sustained attention, organisation, and executive functioning. They may experience difficulty focusing, staying on task, and completing activities. This subtype is often characterised by a tendency to daydream or appear 'lost in thought'.
• Hyperactive-Impulsive Type (ADHD-H): This subtype is marked by pronounced physical restlessness, hyperactivity, and impulsivity. Those with ADHD-H often find it challenging to sit still, may engage in impulsive behaviours, and frequently interrupt others. Hyperactivity can also be internalised and experienced as internalised restlessness. This can lead to difficulties in environments that require sustained calm and focus. 
• Combined Type (ADHD-C): This subtype is a combination of both inattentive and hyperactive-impulsive traits. Individuals with ADHD-C experience difficulties across multiple areas, including attention, impulse control, and hyperactivity. 

How Is ADHD Diagnosed?

The diagnostic process for ADHD is thorough and multifaceted. For a diagnosis of ADHD-I, six or more traits of inattention must be present for children up to the age of 16 years, or five or more for those aged 17 and over. These symptoms must have persisted for at least six months and be inappropriate for the individual’s developmental level. Symptoms of inattention include:

• Failing to give close attention to details or making careless mistakes.
• Having trouble sustaining attention on tasks.
• Not seeming to listen when spoken to directly.
• Failing to follow through on instructions and not finishing tasks.
• Having trouble organising tasks and activities.
• Avoiding or being reluctant to engage in tasks that require sustained effort.
• Losing things necessary for tasks and activities.
• Being easily distracted.
• Being forgetful in daily activities.

For a diagnosis of ADHD-H, six or more symptoms of hyperactivity-impulsivity are required for children up to 16 years old, or five or more for those aged 17 and over. These symptoms must also have persisted for at least six months. Symptoms of hyperactivity-impulsivity include:

• Fidgeting or squirming in seats.
• Leaving seats in situations where remaining seated is expected.
• Feeling restless.
• Being unable to engage in leisure activities quietly.
• Acting as if “driven by a motor.”
• Talking excessively.
• Blurting out answers before questions have been completed.
• Having trouble waiting their turn.
• Interrupting or intruding on others.

For diagnosis of ADHD-C, the criteria for both inattention and hyperactivity-impulsivity must be met. Additionally, several other conditions must be present:

• Several inattentive or hyperactive-impulsive symptoms were present before age 12 years.
• Several symptoms are present in two or more settings (e.g., home, school or work; with friends or relatives; in other activities).
• There is clear evidence that the symptoms interfere with, or reduce the quality of, social, academic, or occupational functioning.
• Symptoms are not better explained by another mental health condition (e.g., anxiety disorder,mood disorder, dissociative disorder, or a personality disorder).

Reflective Questions

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

Understanding ADHD subtypes allows us to appreciate the diversity within the diagnosis and recognise that everyone’s experience of ADHD is unique. By learning more about the nuances of this condition, we can better support those living with ADHD in leading their healthiest and happiest lives.

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