Whilst ADHD and FIbromyalgia are distinct unconnected diagnoses, there is a lot of clinical overlap, particularly from functional medicine perspective. My interest in this started over 10 years ago when I researched under an environmental medicine doctor who specialised in neurodivergent children (Autistic and ADHD primarily). We had noticed so many of the mother’s of these children had diagnoses of CFS/ME or Fibromyalgia, and at the time we were running a lot of lab tests such as the organic acids, GI Effects (CDSAs), mineral tests, genomics, viral panels on these children and screening the mothers too. We found their test results would be identical! -but with very different clinical presentations… and this was all before we understood what ADHD girls really looked like or had any idea of concepts like masking.

The doctor at the time believed that ME or Fibromyalgia was pretty much Autism/ADHD but with a slower adult onset, which at the time was a bold statement to make but I could not unsee this connection. When I started working for a specialist CFS/ME and Fibro clinic (The Optimum Health Clinic) I kept seeing this connection all the time - my patient’s children were often autistic/ADHD.

Connections from research

Clearly I am not the only person suspecting this connection. A study screening 123 adults with Fibromyalgia found that about 45% (nearly half) of these participants met the criteria for a diagnosis of ADHD.

Another study found that 8 out of 10 (80%) of adults diagnosed with ADHD suffer from chronic widespread pain, compared to 17% of neurotypicals. In my clinical and own experience of pain, this ranges from chronic back and neck pain, IBS (gut pain), muscle and joint pain, TMJ, headache and migraines.

Research looking into what might be underlying pain in ADHD lists “centralized sensitisation” and “neuroinflammation” to be driving this – which is what drives pain sensitivity in Fibromyalgia.

The impact of sex and gender differences in ADHD presentation

In childhood, for every 5-10 boys diagnosed with ADHD, only 1 girl is. However in adulthood the rates dramatically drop and the adult male to female ratio is closer to 1:1. So in reality ADHD is not more common in boys than it is girls, it is just hidden in girls - at least until adulthood.

So what happened to all these ADHD girls in the meantime?

The short answer is mainly lost to chronic illnesses with a female bias including Fibromyalgia, CFS/ME, Burnout or other complex psychiatric diagnoses.

Recent studies looking at ADHD in females finds that girls tend to have more internalised traits rather than outwardly showing behavioural problems. Rather than hyperactivity such as ‘climbing on furniture’ or fidgeting, we tend to have an internal mental restlessness, racing thoughts and overthinking. Boys or others on the gender spectrum who do not outwardly express traits may also be missed because the DSM criteria is made up of mainly externally observable ADHD traits and does not appreciate the full ADHD experience. Remember you cannot diagnose what you can’t see!

In addition, AFAB/Internalised phenotypes could be better at hiding their traits - known as masking/camouflaging, in order to fit it, not get into trouble and follow rules and expectations.

Or they may not have been seen because of gendered expectations we project onto children:

That good girls/boys are organised and well behaved, seen and not heard
That girls with mental restlessness and racing thoughts are overly sensitive and anxious. AFAB neurodivergent people are more likely to be misdiagnosed with personality disorders (i.e. borderline or oppositional defiance disorder) and eating disorders than ADHD or Autism.

In addition:

Sex hormones - especially oestrogen, has a huge impact on the ADHD brain

ADHD is directly influenced by oestrogen and progesterone, known as neurosteroids, because in the brain they regulate the activity of neurotransmitters. Oestrogen increases the amount of dopamine that is transmitted, synthesised and reuptaken.

In a typical menstrual cycle when oestrogen levels peak - days 7-14, frequently ADHD females will experience a lessening of their difficulties, as oestrogen starts to drop and progesterone rises (mitigating the effect of oestrogen on dopamine) those with menstrual cycles often report that their ADHD medications aren’t as effective in that part of their cycle.

Similarly with peri and post menopause. Often these hormone swings and decline in oestrogen leads to people feeling their traits the most whilst being unable to mask them any longer.

What is the current understanding of Fibromyalgia?

Even professionals can’t agree! There are no objective biomarkers so it is diagnosed based on exclusion of other conditions that do have blood markers or criteria that are a better fit. It is a highly stigmatised and poorly understood condition. In part due to the complete disinterest in researching female pain.

Fibromyalgia is a condition that affects the whole body and is characterised by widespread pain, fatigue and cognitive problems known as “fibro fog” or brain fog. When you look at what these cognitive issues are they are describing executive functioning difficulties. Deficits in memory, attention and studies even finding slower activity in the prefrontal cortex (the same areas of the brain associated with ADHD).

The mechanism is “central allodynia” or “centralised sensitisation”. What this means is things that aren’t supposed to be painful, are experienced as painful because the central nervous system has become sensitised to it.

The research literature has found a whole host of things as possible contributors to centralised sensitisation including: neuroinflammation, immune dysfunction, adverse life events/trauma, abnormalities in neurochemicals (dopamine, GABA, noradrenaline), oxidative stress and mitochondrial dysfunction.

People with Fibromyalgia often experience limbic system hypervigilance, where things that do not cause stress in the majority brain, do in the Fibro nervous system, creating an emotional sensitivity. This is another overlapping feature with ADHD, where 70% of ADHDers experience emotional dysregulation.

This Fibromyalgia “iceberg” illustrates what clinicians understand about Fibro vs what it actually is.

The current understanding of Fibromyalgia is a very ‘surface level’ understanding of what is actually a very complex neurotype and phenotype.

Clinically, we see personality traits such as high empathy, high masking professions (such as teachers, doctors, therapists and carers) which we know are connected to increased burnout, stress and disconnection from your sense of self.

There is growing evidence that Fibromyalgia is not just pain specific, but there are also sensory perception and processing difficulties across multiple senses which then puts people at risk for developing a more pain-specific profile.

There is also intriguing evidence that there are higher levels of Alexithymia in Fibromyalgia which correlates with how disabling the chronic pain is on their quality of life. We know that ADHDers experience higher rates of Alexithymia (about 41.5% of ADHDers are alexithymic) and this is linked to impulsivity.

Interoception, perceptual and sensory processing differences

One way to understand chronic pain conditions such as Fibromyalgia and also the pain sensitivity in ADHD is through the lens of interoception and sensory processing differences.

Interoception is our 8th sense, an internal sense that allows us to feel our feelings and to respond or interact with our internal and external environment. Receptors throughout our bodies pick up sensory information and send these signals through the vagus nerve and spinal cord to the brain where this information is processed in many areas but especially the insula cortex.

This sensory input could be a physical sense - such as “I’m too cold” or “I’m getting hungry” or it could be an emotion such as “I’m bored” or “I don’t feel safe” and these signals have to be contextualised using memories or past experiences, logic, our expectations (especially when it comes to pain - i.e. “when I pick up a hot cup, the heat may cause pain” and also our cognitive or current emotional state.

The insula then promotes either a reflexive urge, thought or biological action to regulate ourself…. and one of these outputs is pain.

Pain is the immediate ‘danger response’ when the brain has decided the sensory input is a threat.

This ‘sensory processing’ can be slower in neurodivergent people or those with a chronic illness such as Fibromyalgia, as processing is in part an executive function.

Additionally, the same neural pathways that process emotions and feelings (both are sensory) also process pain, so we can see how this signalling might get mixed up. For example when you have the urge to go to the toilet, but it is just nervousness or anxiety. A common phenomenon in my clinic is where changes in air pressure (not usually linked to pain in the majority brain) can lead to migraines in the neurodivergent brain or chronic migraneur.

Good interoceptive awareness is when you can identify what is going on inside your body with a high degree of accuracy. But people with Fibromyalgia and ADHD have higher rates of interoceptive challenges and this can result in many types of sensory inputs being processed differently, misinterpreted as ‘danger signals’ and resulting in pain, or sensory overload, or emotional dyregulation as a result.

The ADHD and Fibromyalgia overlap: An exploration of late diagnosed ADHDers and chronic pain syndromes