Written by Kate Hoad (Occupational Therapist)
There appears to have been increasing stories in popular media on ADHD lately, reporting on greater numbers of ADHD-ers being recognosed, both in children as well as adults. So lets dive into what ADHD is, and why it's important to recognise, understand and treat difficulties that result. The neurobiological basis of ADHD (brain-based differences) People with ADHD often exhibit differences in brain structure and function compared to individuals without it. These brain differences are believed to underlie the core symptoms of ADHD, such as inattention, hyperactivity, and impulsivity. Advanced neuroimaging techniques have provided valuable insights into these neurobiological disparities. Here are some of the key brain differences observed in individuals with ADHD:
Prefrontal Cortex (PFC) Dysfunction
The prefrontal cortex, which is responsible for executive functions like planning, decision-making, and impulse control, shows differences in individuals with ADHD. Reduced activity and connectivity in the PFC have been observed, leading to difficulties in organising thoughts, self-regulation, and maintaining attention on tasks.
Dopamine and Norepinephrine Dysregulation
Neurotransmitters, such as dopamine and norepinephrine, are essential for signalling between neurons in the brain. Research indicates that individuals with ADHD may have imbalances or dysregulation in the levels of these neurotransmitters, which can impact attention, motivation, and reward processing.
Reward Processing Systems
The brain's reward system, involving areas like the ventral striatum and the anterior cingulate cortex, may be affected in ADHD. This could contribute to challenges in prioritizing tasks, staying motivated, and sustaining attention on non-rewarding activities.
Basal Ganglia Abnormalities
The basal ganglia, a group of structures deep within the brain, are crucial for motor control and attention. Studies suggest that abnormalities in the basal ganglia may contribute to the hyperactivity and motor restlessness seen in ADHD.
The cerebellum is traditionally associated with motor coordination, but it also plays a role in cognitive functions. Differences in the cerebellum's structure and connectivity have been linked to difficulties in sustained attention and coordination of cognitive processes in ADHD.
Connectivity and Networks
Brain networks responsible for coordinating different brain regions and functions may also show differences in individuals with ADHD. Altered connectivity within the default mode network (related to self-referential thinking) and the salience network (involved in detecting important stimuli) has been observed in ADHD.
Studies have shown that individuals with ADHD, particularly children, may have slightly smaller total brain volumes compared to neurotypical peers, most prominent in specific brain regions involved in attention, impulse control, and executive functions, such as the prefrontal cortex, basal ganglia, and cerebellum.
It's important to note that while these brain differences are consistently observed in ADHD, they do not provide a definitive diagnosis on their own. ADHD remains a clinical diagnosis based on the presence of specific behavioural symptoms and impairment in daily functioning. Additionally, individual brain differences can vary widely within the ADHD population, and not everyone with ADHD will exhibit the same neurobiological characteristics.
Understanding the brain differences associated with ADHD can help inform treatment approaches and strategies aimed at supporting affected individuals (See next week's blog for further information on treatment strategies).
While the exact cause of these brain differences is not fully understood, it is likely that genetics, environmental factors, and neurodevelopmental processes interact to contribute to the neurobiological basis of ADHD. Emerging genetic studies have identified several genes associated with ADHD, many of which are involved in dopamine signaling and synaptic transmission. Family and twin studies have provided strong evidence for the heritability of the disorder, with estimates of genetic contribution ranging from 70% to 90%.
Furthermore, prematurity, low birth weight, maternal stress during pregnancy, and early exposure to lead have been identified as potential risk factors for ADHD development. Nevertheless, it is crucial to recognise that not all individuals with these risk factors will develop ADHD, indicating the complex interplay of various factors in its presentation.
Diagnostic Criteria and Subtypes:
The diagnostic criteria for ADHD have been refined over time, with the latest version found in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) - this is the medical professions 'bible' of how to recognise underlying mental and developmental conditions. According to the DSM-5, ADHD is categorised into three subtypes:
1. Predominantly Inattentive Presentation (formerly known as Attention Deficit Disorder [ADD])
Characterised by significant difficulties with attention and focus while lacking pronounced hyperactivity and impulsivity.
They often appear forgetful, easily distracted, and may struggle to complete schoolwork or chores
Due to their quiet and less disruptive nature, children with ADHD-PI may go unnoticed or be mislabelled as daydreamers or underachievers
Individuals with ADHD-PI may have trouble sustaining attention, following through on tasks, and organising activities.
Some studies suggest that ADHD-PI accounts for around 25% to 35% of all ADHD cases in children.
2. Predominantly Hyperactive-Impulsive Presentation
In this presentation, hyperactivity and impulsivity are the primary symptoms, while inattention is less pronounced.
Display excessive restlessness, fidgeting, and difficulty remaining seated when expected.
May talk excessively, interrupt others, and find it challenging to wait their turn.
Children with this presentation may engage in physically risky behaviours and be seen as disruptive or "always on the go."
Often struggle with following rules and may have difficulty in social situations due to their impulsive behaviour.
It is estimated that around 5% to 10% of children with ADHD have the predominantly hyperactive-impulsive subtype.
3) Combined Presentation (comprising both inattentive and hyperactive-impulsive symptoms)
Most common form of ADHD. Studies suggest that around 65% to 75% of children with ADHD have the combined subtype.
Involves a combination of symptoms from both the inattentive and hyperactive-impulsive presentations (significant problems with attention, focus, impulsivity, and hyperactivity).
May have difficulty organising tasks, maintaining attention, and controlling impulsive behavior.
This presentation is often associated with more severe impairment and is typically the form of ADHD that comes to clinical attention most frequently.
To meet the criteria for ADHD diagnosis, individuals must have exhibited a persistent pattern of symptoms for at least six months, causing significant impairment in at least two settings (e.g., school, home, work).
Prevalence , differential diagnosis and co-occuring conditions:
ADHD is a relatively common disorder, affecting individuals across cultural and socio-economic backgrounds at a reported rate of 1 in 20 Australians (5%). In recent years, an increased awareness of the disorder and improvements in diagnostic practices have contributed to higher reported prevalence rates - and likely increased stories about 'epidemics' on social and popular media. In essence, there is simply better diagnosis processes, leading to the increased recognition of individuals who have had ADHD all along.
One of the challenges in diagnosing ADHD is its overlap with other psychiatric and developmental conditions. Medical professionals such as psychiatrists and paediatricians must rule out other conditions that can present with similar symptoms, such as learning disabilities, mood disorders, anxiety disorders, and autism spectrum disorders, to ensure an accurate diagnosis. This process involves a comprehensive assessment, including interviews with the individual, parents, and teachers, and the use of standardised rating scales and behavioural observations. Sometimes this is completed by a psychologist.
ADHD frequently co-occurs with other mental health conditions, such as Autism (this is currently reported to be co-occuring in 70-80% of cases, which is certainly my experience clinically as an OT), oppositional defiance disorder (ODD),anxiety disorders, depression, and substance use disorders. Comorbidities can complicate the clinical picture, affect treatment outcomes, and increase the burden on affected individuals and their families. It is important for clinicians to look into all possibilities.
Treatment Approaches (Further information in next week's blog!):
The management of ADHD typically involves a multimodal approach that combines medication, behavioural interventions, and therapies such as psychoeducation or Occupational Therapy. Stimulant medications are the most commonly prescribed medications for ADHD. These drugs work by increasing dopamine and norepinephrine levels in the brain, improving attention and impulse control. Non-stimulant medications are alternative options for individuals who do not respond well to stimulants or have specific contraindications such as heart problems.Behavioral therapy aims to teach coping strategies, organizational skills, and time management techniques, while also addressing specific challenges related to ADHD symptoms. Parent training programs can help parents develop a better understanding of the difficulties inherent in ADHD (i.e., generally, that they're not 'being bad') and help them to develop effective parenting strategies to support their children with ADHD.
ADHD was once thought to be a childhood-limited disorder; however, research has now established that it often persists into adolescence and adulthood, and in fact that many adults continue to have difficulties related to ADHD, but were not diagnosed as children. Adult ADHD is characterised by similar symptoms to those observed in children, albeit with some differences related to developmental challenges and the coping mechanisms individuals develop over time. Generally, when an adult is diagnosed with ADHD, it is likely they have reached their threshold for coping with the intricacies and moving parts of life. This commonly occurs when there are big life transitions away from a structure and routine that has been assisting the individual to cope, such as:
Transition to adulthood from school
Relationship changes (new live-in relationship, marriage breakdown)
Having children (therefore increasing responsibility)
The recognition of adult ADHD has grown in recent years, leading to increased research and awareness of the unique challenges faced by adults with the disorder. Diagnosis and treatment for adult ADHD are essential to improving functioning and quality of life in this population.
ADHD is a chronic condition that can significantly impact various aspects of an individual's life, including academic and occupational achievements, social relationships, and emotional well-being. Research has shown that individuals with untreated or poorly managed ADHD are at a higher risk for academic underachievement, job instability, and involvement in legal issues.
However, early diagnosis and appropriate interventions, such as behavioral therapy, educational support, and, when necessary, medication, can lead to better long-term outcomes. Treatment plays a crucial role in improving symptom management, executive functions, and overall quality of life for individuals with ADHD.
Overall, ADHD is a complex neurodevelopmental disorder with the risk of significant implications for affected individuals and society as a whole if individuals remain undiagnosed and untreated. The latest evidence supports a multifactorial etiology involving genetic and environmental factors, with neurobiological differences underlying ADHD core symptoms. Early diagnosis and comprehensive interventions are crucial to optimising long-term outcomes for individuals with ADHD, both during childhood and into adulthood. With ongoing research and advancements in treatment approaches, we can enhance our understanding of, and continue to improve the lives of those living with ADHD.