Fatigue in ADHD & Autism: What are we noticing and why does it happen?
Here at Vitality360, we have been witnessing an emerging trend of a significant percentage of our client group who come to us as experts in fatigue and pain management, also reporting suspected or diagnosed ADHD/autism. People with ADHD and autism often report significant fatigue, a profound mental and physical exhaustion that isn’t just being “lazy” or tired. This fatigue usually comes from a combination of biological, cognitive, and environmental factors rather than any single cause. In this blog, we look at some of the key reasons this happens, with a focus on shared characteristics as well as those unique to ADHD or autism.
We have been treating people with fatigue symptoms from a range of causes for 13 years. This means we understand how important it is to include the neurodiversity aspect of a person’s profile, even if they only suspect they may be neurodivergent. It means we can understand more holistically the causes of fatigue from this perspective, whilst embedding it in all our expertise in fatigue management. At the end of this blog, we consider what some of these rehabilitation interventions may look like. If you would like to discuss your situation, please book a free 15-minute call via our website.
Shared Factors Contributing to Fatigue (ADHD & Autism)
ADHD-specific fatigue factors
Hyperactivity & “Crash”: By definition, ADHD involves hyperactivity (in many, though not all, cases) and impulsivity. This can mean a person is constantly mentally and/or physically restless, their brain is “always on.” All that extra movement and thought consumes energy. Often, people with ADHD go through the day expending high levels of energy, only to “crash” later with heavy fatigue. Hyperactivity also makes it hard to wind down at night, contributing to the sleep issues. In short, the ADHD brain can run like a motor on overdrive and then hit a wall of exhaustion.
Attention Switching & Mental Effort: The ADHD brain has trouble sustaining attention on demand. Starting, stopping, and re-focusing on tasks (especially uninteresting ones) requires effortful concentration. This stop-start cycle of attention, constantly pulling your mind back on track, is very tiring. Frequent task-switching or struggling to finish tasks due to distractibility leads to mental fatigue as the brain is overworked by continual reorientation. Researchers note that managing many small transitions or tasks can lead to “executive functioning fatigue” in ADHD - essentially, the brain’s energy budget for focus gets depleted faster.
Reward System Differences (Dopamine): ADHD is associated with atypical dopamine regulation in the brain’s reward pathways. Dopamine is a neurotransmitter that helps with motivation and alertness. In ADHD, lower dopamine levels means it’s harder to feel motivated and rewarded by routine tasks. This makes every activity feel like it takes more effort, which in turn increases the sense of fatigue. In essence, the ADHD brain has to “push” itself more to get things done due to this reward/motivation gap, which can be exhausting, especially when sustained over long periods.
Autism-specific fatigue factors
Social Exhaustion (Social Fatigue): Social interactions can be uniquely draining for autistic individuals. Reading body language, interpreting tone of voice, knowing when to speak – these “unspoken” social rules don’t come instinctively and must be analysed intellectually. Even pleasant socialising can feel like work. Autistic people often report that even brief social encounters leave them mentally wiped out. One reason is that they may be consciously second-guessing their own expressions or others’ meanings in real time. Additionally, social settings often come with a lot of sensory input (background noise, multiple people talking, etc.), which can lead to sensory overload and heighten fatigue. This is why many autistic adults need significant alone time after social events – it’s a recovery period for their overtaxed brains.
Need for Routine vs. World’s Unpredictability: A hallmark of autism is a preference for structure and routine. Sudden changes, uncertainty, or having to adapt on the fly can be extremely stressful. Constantly having to adjust to new schedules, environments, or expectations uses a lot of mental energy. The world rarely conforms to one’s preferred routine, so autistic individuals often find themselves struggling to create order in chaos. This mismatch – needing predictability in an unpredictable world – is exhausting and can induce anxiety. For example, an autistic person might handle big changes (like a new job or travelling) with great difficulty; the effort of adjusting to the new situation can quickly lead to shutdown or burnout. In those with both autism and ADHD, clinicians have noted that the autistic desire for sameness conflicts with ADHD’s tendency toward spontaneity, resulting in internal tension and fatigue from managing change.
Deep “Detail-Oriented” Processing (Cognitive Style): Autistic brains often process information in a bottom-up, detail-focused way, meaning they notice and analyse lots of details that others might gloss over. While this can be a strength, it also means the autistic mind is doing more processing at any given moment. They may deeply ponder information, scenarios, or problems to the point of information overload. For instance, filtering through a noisy environment or absorbing a large amount of new information can lead to mental exhaustion because the brain processes every detail. This cognitive style – methodical, thorough processing – can make complex or high-stimulus situations especially tiring, as if a computer is running too many heavy programs at once and slowing down. It’s not that they cannot do the task; it’s that doing it the way their brain is wired takes more out of them.
When ADHD and autism overlap: The compounding effect
Some people are both autistic and have ADHD (a dual diagnosis often nicknamed “AuDHD”. In these individuals, the fatigue factors of both conditions can stack up and interact, making energy issues even more pronounced. In fact, life with co-occurring ADHD and autism is sometimes described as a constant push-and-pull between conflicting needs, which can lead to frustration, exhaustion, and burnout.
Double Sensory-Attention Drain: An AuDHD person might experience heightened sensory overload (from the autism side) and extreme distractibility (from the ADHD side). They are inundated by sensory input while simultaneously struggling to focus – a double-whammy for the brain’s energy resources. It’s easy to see why this would quickly deplete someone.
Social Masking + Attention Dysregulation: They may find social situations especially exhausting because not only are they potentially masking autistic traits to fit in, they’re also fighting the ADHD tendency for their mind to wander. Holding a conversation while internally suppressing stims or anxiety and trying to stay on topic is enormously taxing, reaching an overwhelming point faster than it would with either condition alone.
Overlapping Sleep and Health Challenges: The sleep disturbances and co-occurring conditions (like anxiety or mood disorders) common in ADHD or autism can also compound in AuDHD individuals. For example, if ADHD-related insomnia is also met with autistic circadian rhythm differences, getting restful sleep may be even harder. Poor sleep then feeds back into worse attention, sensory tolerance, and emotional regulation the next day, creating a vicious cycle of fatigue.
Dietary challenges: A 2016 systematic review and meta-analysis by Nazar et al. revealed that people with ADHD are nearly four times more likely to develop an eating disorder. Conversely, when looking at individuals with diagnosed eating disorders, they were more than twice as likely to have ADHD. This relationship exists across different eating disorder presentations and throughout the lifespan. Our specialist dietitian Sue Luscombe comments:
"This is an excellent article exploring some of the differences in ADHD and autism with eating. Understanding these differences is very helpful in providing the most appropriate support to our clients and patients. Dietary challenges and eating differences: Many autistic people and those with ADHD experience eating in ways that don’t fit typical expectations. Some challenges include sensory sensitivities: strong reactions to textures, smells, or flavours can make many foods difficult to eat. Also, body awareness (interoception): some people don’t notice hunger or fullness, leading to skipped meals or overeating. Lastly, anxiety and rigidity: fear of new foods or a strong preference for sameness can make variety feel unsafe. Medication for ADHD can also change or reduce appetite and intake. All these factors will increase the risk of nutritional inadequacies.."
In summary: Fatigue in ADHD and autism is very real – it’s the result of brains working much harder to manage attention, filter sensory input, regulate emotions, and meet everyday demands. This isn’t due to lack of will or laziness at all. On the contrary, neurodivergent individuals are often expending extra effort to function in a world not built for their neurotype. Understanding these fatigue factors can foster more empathy and highlights why strategies like “energy budgeting,” sensory regulation, routine scheduling, and ample rest are so important. By respecting their unique energy needs (for example, taking breaks, using noise-cancelling headphones, or having flexible schedules), people with ADHD and/or autism can better manage their fatigue and thrive in daily life.