Ah, interesting.

Chronic fatigue is such a slippery diagnosis. This is just my armchair expert opinion but I think chronic fatigue is sorta like a wastebasket diagnosis - when you're dealing with a set of symptoms that are difficult to pinpoint then you often get put into these diagnoses. That's not to say that something like chronic fatigue or borderline personality disorder doesn't exist or have real-world impacts on people but it can be really easy for doctors to just shrug their shoulders and give someone a "Too hard, nothing I can do - sorry!" diagnosis.

So for chronic fatigue and ADHD (any other diagnoses or suspected diagnoses btw?) there's a few things that I'd want to eliminate:

First off there's dietary stuff. It's not uncommon for people on stimulants to have a markedly reduced appetite. If you notice that you're skipping meals regularly or only eating small meals then, in no particular order I'd be looking at: Vitamin B levels (especially if you're vegetarian or vegan), iron deficiency (especially if you're AFAB), vitamin D, and chronically low protein intake.

While the symptoms of low protein intake are really hazy and difficult to figure out, protein provides the essential building blocks for neurotransmitters and if you're low in it for an extended period and you're an ADHDer then at some point your brain's fuel tank is gonna start running low and that could be the cause of a relapse in chronic fatigue symptoms.

The easy fixes/diagnostic probes are to supplement your diet here.

Arguably, most people are low in Vitamin D in the developed world and low to moderate supplementation is of minimal concern.

Vitamin B levels are of particular importance if you're a vegetarian or vegan, especially B12. Low to moderate supplementation is of minimal concern here as well.

Supplementing iron in the case of anaemia takes a few weeks before you'd expect to see significant improvements, so if you choose to do this then I'd give it a solid month of fairly consistent supplementation before I'd expect to see results.

Low protein intake would be easy to spot by journalling a couple of day's worth of your diet and doing napkin math. Or you could just throw some protein powder into a smoothie for breakfast every day for a week or two and see if you notice any changes.

The next thing I'd look at is if there are any problems with your sleep because sleep deprivation is really hard on ADHDers and it's very likely to cause an aggravation in symptoms. If your chronic fatigue symptoms are, in part or wholly, due to ADHD symptoms (if you're combined type or particularly if you're inattentive type) then this is definitely worth considering.

Have you changed your lifestyle or started working late shifts at work?

Are you taking meds too late in the day and is this disrupting your sleep?

Do you have any breathing problems such as asthma or suspected sleep apnoea?

Note that you might have chronic low-grade asthma symptoms that are going untreated which may be causing symptoms that are mimicking chronic fatigue. A long-acting beta antagonist used regularly over a couple of days would eliminate this as a possibility, as would corticosteroids but they take a lot longer to kick in although they're far more suitable for maintenance.

Also note that sleep apnoea can be silent so while snoring and audible breathing irregularities are a good indication of sleep apnoea, the absence of them isn't proof that you don't have it. Being overweight is a major risk factor for this so if you've had significant changes in your weight then that might make this worth considering.

The next thing I'd be looking at is an increase in depressive symptoms. If we're working with a dopaminergic or noradrenergic hypothesis for depression then a stimulant would have alleviated the depressive symptoms and, if this was a causative factor for your chronic fatigue, then you would have seen a reduction in the chronic fatigue symptoms which seems to track based on what you've reported.

This one is above my pay grade but serotonin has an inhibitory effect on dopamine in certain parts of the brain. If you've gone onto an antidepressant and noticed an increase in your chronic fatigue symptoms then that could be a cause.

Conversely, if you're experiencing a drop in serotonin then this may also be a cause for aggravation in depressive symptoms which could have a flow-on effect with chronic fatigue symptoms.

Last candidate to consider is norepinephrine. Are you taking any blood pressure medications or an ADHD med like guanfacine or clonidine? These especially can impact norepinephrine and if you've ever taken too much of something like clonidine then you've had a crash course in what chronic fatigue can feel like.

The final thing that may be of relevance here is catatonia. This is not something which is prevalent in ADHDers however its prevalence is quite high amongst autistic people and with certain mental illnesses, so if you have comorbidities here or suspected comorbidities then that would make this next bit worth considering. Otherwise, probably not.

Catatonia is poorly understood by psychiatrists and it's even worse in the general population. I won't belabour the point but certain types of catatonia can closely resemble chronic fatigue symptoms.

Stimulant meds do treat catatonia, mostly, however it's a mixed bag and they can aggravate catatonia and its underlying causes as well.

Catatonia is chronically underserved in the literature and I'm unaware of any long-term studies that have looked at treating catatonia with stimulant monotherapy so, while stimulants have been shown improve acute episodes of catatonia in preliminary studies, I would suspect that in the long term they would either exacerbate them or lose efficacy for treating those symptoms. But that's more of a hunch based on inference than anything where I point to studies to prove my point directly.

I've been threatening to make a masterpost on catatonia for a while now and I haven't gotten around to it...

Long story short, if you suspect it could be catatonia then a diagnostic probe of lorazepam is the gold standard (you'd probably need an open minded psychiatrist to prescribe this). Zolpidem appears to work about as well as lorazepam and it's easier to get your hands on for a diagnostic probe (in some countries it might be easier to get zopiclone which is essentially the same for these purposes.) Longer term treatment and management of catatonia is complex but if you are at the point of considering a diagnostic probe then I can provide you with more information about this - just ping me or DM me.

So, TL;DR:

• Get a blood test, if possible. Check your levels of iron and vitamins B & D in particular, and other likely candidates for chronic fatigue such as hormone function.

• Add extra protein into your diet for a while

• Eliminate breathing problems as a cause (asthma, OSA etc.)

• Eliminate sleep problems as a cause (OSA, lifestyle factors)

• Eliminate low blood pressure as a cause (BP meds, hypotension - get your BP tested)

• Speak to a psychiatrist about any recent changes to your medication regime that may be suspect, especially re: antidepressants, BP meds, and ADHD meds such as clonidine and guanfacine

• Speak to a psychiatrist about striking the right balance of serotonin, dopamine, and norepinephrine (they should be doing this anyway but yeah...), adjust meds accordingly

• Possibly consider catatonia, especially if you are autistic (or suspect that you are) or if you have comorbid mental illness, especially psychosis, schizophrenia and related disorders, bipolar and related disorders.

Of course I'm no doctor, I'm just some nerd on the internet, so treat everything I've said with the importance that an anonymous, unqualified stranger on the internet deserves. I haven't gone into a lot of other factors that may be contributing to your chronic fatigue such as post-viral syndrome (especially long COVID) or things like Lyme disease or chronic rickettsiosis so don't take what I've said as being an exhaustive list either. But this is mostly just the basic stuff which a diligent psychiatrist would want to rule out so if you're able to get a head start on it then it's going to make the best use of your time with them.

Also feel free to take any questions I've posed above as being something for you to consider or as a conversation to bring to your doctor; don't go sharing information when you don't feel comfortable in doing so or if it's going to compromise your safety or wellbeing.

I hope that there's something in here which is useful to you but more than that I hope that your health improves.