Anxiety Fatigue: Why Worry Drains You, From the Studies

Anxiety fatigue is the exhaustion that comes with long spells of anxiety, and it is common: being easily fatigued is one of the listed symptoms of generalised anxiety disorder. Studies point mainly to broken sleep, which anxiety and insomnia each make worse, plus the effort of constant vigilance. The cortisol story is far less tidy than most pages claim.

On this page: five cited findings on how anxiety and poor sleep feed each other, with sample sizes, the cortisol result that contradicts the usual story, and a sleep and worry diary to take to a GP.

Most of the pages ranking for this phrase belong to online therapy services, and they tend to say the same three things: stress hormones, adrenaline, see a therapist. That last part is reasonable. What they skip is the actual research, how big the effects are, and where it contradicts the neat version. This page puts the numbers in, with every study linked, and is honest about the gaps. If the foggy thinking is the part that bothers you most, our companion piece on whether anxiety can cause brain fog covers the memory and concentration side in detail.

Why does anxiety make you so tired?

Partly because tiredness is built into how anxiety is defined. The US National Institute of Mental Health lists trouble falling or staying asleep, feeling fatigued, and aches or muscle tension among the signs of generalised anxiety disorder, and the NHS describes the condition as anxiety about a wide range of things that lasts, rather than about one event. Exhaustion is not a side issue in that picture. It is on the list.

How common is it? A systematic review published in BMC Psychiatry in 2026 pulled together 46 papers on fatigue across common mental health conditions, anxiety disorders among them, and found prevalence anywhere from 18% to 100% depending on the study and how fatigue was measured. That range is too wide to quote a single figure, and the authors’ own conclusion is the useful part: fatigue turns up across so many conditions that they treat it as a shared symptom rather than a marker of any one of them. So feeling wiped out tells nobody, including you, what is behind it.

Sleep is the most measured route. A 2025 meta-analysis in the Journal of Psychosomatic Research pooled five studies covering 5,875 people with generalised anxiety disorder and put the prevalence of sleep disturbance at 72%. Look at the uncertainty around that figure, though: the 95% interval runs from 28% to 99%, because the five studies disagreed a lot. “Most people with GAD sleep badly” is fair. “Exactly 72%” is not.

How do anxiety and poor sleep feed each other?

In both directions, and this is the best supported part of the whole topic. Researchers test it by measuring anxiety and sleep at one point, then checking who develops the other problem later. The answer keeps coming back as a loop rather than a one way street.

Study	Who was followed	Direction tested	What it found
Jansson-Fröjmark and Lindblom, 2008	1,812 Swedish adults at baseline, 1,498 a year later	Anxiety, then new insomnia	Odds of new insomnia 4.27 times higher with high anxiety
Same study	Same group	Insomnia, then new high anxiety	Odds 2.30 times higher
Hertenstein and colleagues, 2019	13 studies, 181,798 people; 6 studies for anxiety	Insomnia, then later anxiety	Odds 3.23 times higher (95% range 1.52 to 6.85)
Sleep Medicine, 2024	Middle aged and older adults in the community	Sleep disturbance, then anxiety	Risk 1.89 times higher
Same study	Same group	Anxiety, then sleep disturbance	Risk 1.20 times higher

The interesting disagreement is about which half of the loop is stronger. The Swedish study found anxiety predicting new insomnia more strongly than the reverse, 4.27 against 2.30. The 2024 study in older adults found the opposite, 1.89 for sleep problems leading to anxiety against 1.20 the other way. Different ages, countries and questionnaires probably explain a lot of that, and nobody has settled it. What both agree on is the part that matters to someone lying awake at 3am: each problem raises the odds of the other.

Sleep studies in the lab back up the self reports. A meta-analysis of polysomnography research in Psychological Bulletin, the kind of study where people sleep wired to sensors, found that anxiety disorders, like several other mental health conditions, showed changes in how deep sleep was and in REM sleep, and concluded that a broad sleep disturbance is shared across many disorders rather than being unique to one. Our page on what lost sleep does to thinking covers the next step in that chain.

Is cortisol really the reason anxiety is exhausting?

Plenty of pages say so, as though the case were closed. The research is messier. A 2017 meta-analysis in Psychoneuroendocrinology pulled together studies of cortisol responses to a stressful task across psychiatric conditions. For anxiety disorders it had 9 studies and 732 people, and the result split by sex: women with a current anxiety disorder showed a blunted cortisol response, while men with social anxiety showed a raised one. “Anxiety floods you with cortisol until you are exhausted” does not survive contact with that finding.

The nervous system side is more consistent. A 2014 meta-analysis in Frontiers in Psychiatry found that people with anxiety disorders have lower heart rate variability than people without, a small to moderate difference (Hedges’ g of 0.29 to 0.45 depending on the measure). Lower variability is read as the calming, vagal branch of the nervous system doing less of the braking. It fits the idea of a body that stays switched on, but it is a correlation, and no study has shown that this is what makes people feel tired.

So the honest summary is that sustained arousal is real and measurable, sleep loss is real and measurable, and the link from either to the feeling of exhaustion is plausible but not proven step by step. Anyone who tells you the precise hormone responsible is ahead of the evidence, and anyone selling a supplement to fix that hormone is further ahead still.

Why does anxious tiredness hit thinking so hard?

Because worry uses the same limited attention that thinking needs. The leading account, attentional control theory, holds that anxiety costs effort more than it costs accuracy: people keep their performance up by trying harder, and pay for it in tiredness. Our anxiety and brain fog page sets out those studies and their effect sizes. Add a short night on top and the same task costs more again. The lab studies behind that idea, including the Paris experiment that tracked a brain chemical across a working day, are explained in our walk through the cognitive fatigue research.

That is also why anxious tiredness can feel different from the tiredness after a long walk. People often describe it as being wired and drained at once: too alert to rest, too spent to concentrate. It overlaps heavily with what we describe in what being mentally tired means and with the longer stress picture in our page on nervous exhaustion. Physical aches and muscle tension are on the NIMH symptom list too, though they have had far less study as a cause of fatigue than sleep has.

What does the evidence say helps with anxiety fatigue?

The sleep half of the loop has the strongest trial evidence. A meta-analysis of randomised trials by Scott and colleagues in Sleep Medicine Reviews, 2021 looked at 65 trials with 8,608 participants in which an intervention improved sleep, and asked what happened to mental health. Anxiety fell by a medium sized amount (g = 0.51), and the bigger the improvement in sleep, the bigger the drop. The trials varied a lot, so the size is an average across very different studies, but the direction was consistent.

For anxiety itself, the UK guideline is NICE guidance CG113, which sets out a stepped approach for generalised anxiety disorder: information and monitoring first, then low intensity psychological help such as guided self help, and then, if that has not been enough, a choice of cognitive behavioural therapy, applied relaxation or medication. Which step fits whom is a conversation with a GP or a therapist, not something a website can decide. What the guideline does not include is a supplement, a detox or a six question online quiz, which is a useful filter for the advertising that follows this search around.

Fatigue is rarely a trial’s main outcome in anxiety research, so there is little direct evidence on what lifts the tiredness itself. The reasonable reading is indirect: in those trials, when sleep improved, anxiety tended to improve with it. A sleep and worry diary, like the one on this page, gives a clinician something concrete to look at instead of “I am tired all the time”.

When is tiredness with anxiety worth a GP appointment?

When it has gone on for weeks, or it is getting in the way of work or home life. The NHS advises seeing a GP if you have felt tired for several weeks with no obvious reason. Tiredness and anxiety can both come from conditions that are easy to miss when stress seems to explain everything, including anaemia, thyroid problems, diabetes and sleep apnoea, and those are usually checked with simple blood tests or questions. Our guide to extreme fatigue with brain fog walks through what a GP is likely to ask.

Anxiety itself is treatable, and needing help with it is common, not a failure. If anxiety comes with low mood, hopelessness or thoughts of self harm, speak to a doctor now, or in the UK call 999 or Samaritans on 116 123, rather than waiting for a routine appointment.

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This article is general information, not medical advice, and is not a substitute for care from a qualified healthcare professional. Speak to your doctor about your own situation.