Understanding Fatigue: Mechanisms and Challenges Across Conditions, including Neurodiversity

As a clinician specialising in fatigue, I frequently reflect on these questions:

• Why do some individuals experience fatigue more severely or persistently than others?

• Are there identifiable underlying mechanisms?

• What functional and psychosocial challenges arise from chronic fatigue?

• How can targeted interventions best support those affected?

Early in my career, my clinical focus cantered on Post-Viral Fatigue (PVF) and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Over time, my interests expanded to fatigue associated with other clinical conditions, including rheumatologic disorders, cancer, acquired brain injury, multiple sclerosis, and menopause. While the pathophysiological mechanisms differ across these conditions—ranging from immune dysregulation and neuroinflammation to hormonal imbalances—the functional, cognitive, and psychosocial consequences of fatigue often overlap. This has enabled me to translate therapeutic strategies across diverse patient populations effectively.

During the early COVID-19 pandemic, attention returned to post-viral fatigue, an area where established clinical frameworks could immediately be applied. At Vitality360, we dedicated substantial resources to education, assessment, and interventions, supporting hundreds of clients whose daily functioning had been disrupted by fatigue.

As the acute post-pandemic demand decreased, our focus broadened again to fatigue across a range of health conditions. One emerging area of interest is fatigue in neurodivergent populations, particularly Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). This topic featured prominently in our 2023 Fatigue Conference, and subsequent research and clinical observations have confirmed its importance.

Clinical Observations and Service Development

Over the past 12 months, we have observed an increasing proportion of clients presenting with fatigue who have ADHD or ASD diagnoses. A recent internal audit indicated that 22% of clients had a confirmed or suspected neurodivergent diagnosis. This trend has been reflected in discussions during clinical supervision, professional development sessions, and recent conferences.

Our team has since attended multiple specialised webinars, including sessions at the Health and Wellbeing at Work Conference and the VRA Conference 2024, deepening our understanding of neurodivergence-related fatigue. These insights prompted us to explore whether we could provide a specialised clinical service for this population.

Neurodivergence and Fatigue: Mechanistic Considerations

Fatigue in individuals with ADHD or ASD is multifactorial, involving cognitive, emotional, sensory, and physiological domains.

1. Cognitive Load and Executive Dysfunction

• Executive function deficits: Individuals with ADHD or ASD frequently experience difficulties with planning, task-switching, prioritisation, and organisation. These persistent cognitive demands increase mental effort and cognitive fatigue.

• Hyperfocus or perseverative thought: ADHD may involve intense periods of hyperfocus, whereas ASD may involve repetitive or detail-oriented thinking, both of which are mentally exhausting.

2. Sensory Processing and Overload

• Autism: Heightened sensitivity to sensory stimuli (auditory, visual, tactile) leads to overstimulation and cumulative cognitive and physiological fatigue.

• ADHD: While sensory hypersensitivity is less common, difficulties with selective attention and distractibility impose significant cognitive strain.

3. Emotional Regulation and Psychosocial Stress

• Emotion regulation deficits: Increased effort is required to manage affective responses and social expectations, particularly in non-accommodating environments.

• Chronic stress and anxiety: Persistent environmental and social demands contribute to allostatic load, a known driver of fatigue.

4. Sleep Dysregulation

• ADHD: Sleep disturbances, including delayed sleep onset, fragmented sleep, and irregular circadian rhythms, are prevalent and exacerbate fatigue.

• Autism: Sleep difficulties are frequently linked to melatonin dysregulation or heightened anxiety. Poor sleep directly worsens fatigue.

5. Pharmacologic and Comorbid Influences

• Stimulant medications for ADHD can produce rebound fatigue or sleep disruption.

• Co-occurring psychiatric conditions, including anxiety and depression, commonly observed in ADHD and ASD, further exacerbate fatigue.

6. Social and Environmental Exertion

• Masking in Autism: Conscious efforts to mimic neurotypical behaviour require sustained cognitive and emotional energy, which can lead to exhaustion.

• Sustained attention in ADHD: Maintaining focus in under-stimulating or socially demanding environments is energetically costly.

A new service

From November 2025, we are launching a new service dedicated to supporting neurodivergent individuals experiencing fatigue, integrating evidence-based approaches with practical strategies to address the multifactorial nature of fatigue in ADHD and ASD. This initiative represents the next step in our ongoing commitment to understanding and mitigating the impact of fatigue across diverse clinical populations.

By Beverly Knops, Managing Director and Specialist Occupational Therapist in Fatigue Management