Introduction

A fibromyalgia diagnosis goes back to the 1600s. Other names for fibromyalgia are rheumatism, fibrositis, and muscular rheumatism. It’s an inflammatory disease.

Back in early times, physicians couldn’t find evidence of inflammation under those names. So a new medical condition arose called fibromyalgia. Translated from Greek, it means “pain in the muscles and tissue.”

Even though a fibromyalgia diagnosis is still difficult to ascertain today, there have been fantastic advancements. New research helps doctors and patients much more today.

Fibromyalgia tender points are the specific areas that are painful – close to the joints but not the actual joints themselves. Just poking at someone with fibromyalgia can cause them to flinch in pain.

What Is Fibromyalgia?

Fibromyalgia is a long-term condition that causes widespread pain throughout the body, along with fatigue, sleep problems, and difficulty with memory and concentration. It affects an estimated 2 to 4 percent of adults worldwide, and it is diagnosed far more often in women than in men, though researchers now think men may be underdiagnosed rather than genuinely less affected.

For many years, fibromyalgia was poorly understood and often dismissed. That has changed. Researchers now classify it as a disorder of pain processing, sometimes called central sensitization or nociplastic pain. In plain terms, the nervous system appears to amplify normal pain signals. The volume knob on pain is turned up, so sensations that would register as mild pressure for most people can register as real pain for someone with fibromyalgia.

This is an important distinction. Fibromyalgia is not a disease of inflammation, and it is not a form of arthritis. It does not damage joints, erode cartilage, or cause the visible deformities seen in rheumatoid arthritis. Blood tests and imaging scans typically come back normal, which is part of why the condition went unrecognized for so long. Normal test results do not mean the pain is imagined — they simply mean the problem lies in how pain is processed rather than in the tissue itself.

Fibromyalgia is also distinct from chronic fatigue syndrome, now more commonly called myalgic encephalomyelitis (ME/CFS). The two conditions share symptoms such as fatigue and unrefreshing sleep, and a person can be diagnosed with both, but they are separate diagnoses with different defining features. In fibromyalgia, widespread pain is the central symptom. In ME/CFS, the defining feature is a severe worsening of symptoms after exertion, known as post-exertional malaise.

What Causes Fibromyalgia?

There is no single known cause of fibromyalgia. Current research points to a combination of factors that together change how the brain and spinal cord process pain signals.

Changes in pain processing

The most consistent finding in fibromyalgia research is that the central nervous system becomes more sensitive to pain over time. Studies using brain imaging have found differences in how people with fibromyalgia respond to pressure and other stimuli compared with people who do not have the condition. Researchers have also found altered levels of certain neurotransmitters involved in pain signaling. The result is a lower pain threshold and pain that persists without an obvious injury to explain it.

Genetics

Fibromyalgia tends to run in families. Having a close relative with the condition raises a person’s likelihood of developing it, which suggests inherited factors affect how the nervous system handles pain. No single gene has been identified, and genetics alone do not determine who develops fibromyalgia.

Physical or emotional stress as a trigger

Many people can point to an event that preceded their symptoms. Commonly reported triggers include:

  • A physical injury, particularly to the neck or back, or a motor vehicle accident
  • A viral or bacterial infection
  • Surgery
  • Childbirth
  • A period of severe or prolonged emotional stress
  • Significant psychological trauma

Not everyone can identify a trigger, and many people develop symptoms gradually with no clear starting point.

Sleep disruption

The relationship between fibromyalgia and sleep runs in both directions. Pain makes it harder to sleep, and poor sleep makes pain worse. Studies have found that people with fibromyalgia often have disrupted deep sleep, and research in healthy volunteers has shown that depriving people of deep sleep can produce fibromyalgia-like pain and tenderness. Sleep disturbance appears to be part of the mechanism, not just a consequence.

Other conditions that often occur alongside fibromyalgia

Fibromyalgia frequently appears in people who already have another chronic condition, including rheumatoid arthritis, lupus, osteoarthritis, irritable bowel syndrome, migraine, temporomandibular joint (TMJ) disorders, anxiety, and depression. Having one of these does not cause fibromyalgia, but the overlap is common enough that doctors screen for it. Importantly, a person can have fibromyalgia and another condition at the same time — one diagnosis does not rule out the other.

What Are Fibromyalgia Tender Points And Where Are They Located?

Tender points are randomly located. They are just that, sore, tender points all over the body. Doctors recognized 18 of these tender points, and if 11 of them tested positive for sensitivity, a person was then diagnosed with fibromyalgia.

Location of Tender Points

The fibromyalgia tender points where muscular pain and fatigue occur:

Location of Tender Points

  • Lower neck in front
  • The edge of the upper breast
  • The arm near the elbow
  • Knee
  • The base of the skull in the back of the head
  • Upper outer buttock
  • Hip bone
  • Back of the shoulders
  • Back of the neck

Fibromyalgia As a Joint Disease

It is not what fibromyalgia is, though. It is not a true form of arthritis as some people imagine, and it does not cause deformities of the joints.

When the doctor presses the tender point, it is painful. Apart from pain, fibromyalgia can also cause poor concentration or forgetfulness, stress, low mood, worry, tingling, or numbness and swelling of the hands and feet.

The numbness and tingling are known as paresthesia. There are several reasons people could experience numbness or tingling hands, feet, and legs, and fibromyalgia is only one of them.

Fibromyalgia Pain Points in the Hands

There aren’t any specific surgical treatments to treat it. There are other conditions present, though, at the same time, might benefit from surgical treatments.

Rheumatologists might be able to help with diagnosing fibromyalgia and recommend medications, some exercises, and other treatments that can help with fibromyalgia.

Fibro-related hand pain can even occur when you aren’t using your hands. You might feel pain just by reaching for an object or picking something up.
The muscles in the hands are different from those in our legs and arms. The pain we experience might make us think it’s in our joints rather than the tendons and muscles.

Common Triggers and Flare-Ups

Fibromyalgia symptoms rarely stay the same from day to day. Most people experience flare-ups — periods when pain, fatigue, and mental fog intensify — followed by stretches when symptoms settle. Learning what sets off a flare is one of the most useful things a person can do.

Frequently reported flare triggers include:

  • Poor or disrupted sleep, including a single bad night
  • Physical overexertion, especially doing too much on a good day
  • Emotional stress, including positive stress such as travel or holidays
  • Weather changes, particularly cold, damp conditions and shifts in barometric pressure
  • Hormonal changes, including menstrual cycles
  • Illness or infection, even a common cold
  • Changes to routine, such as a disrupted sleep schedule or a skipped meal
  • Inactivity, since prolonged rest tends to increase stiffness and pain

Keeping a simple symptom diary for a few weeks — noting sleep, activity, stress, and pain levels — often reveals patterns that are not obvious in the moment.

The Full Symptom Picture

Fibromyalgia produces a wide range of symptoms that extend well beyond pain. Severity varies from person to person, and symptoms often fluctuate.

Pain

The hallmark symptom is widespread pain lasting three months or longer. People describe it as a constant dull ache, burning, throbbing, or stabbing. It is typically felt on both sides of the body and both above and below the waist. Morning stiffness is common, as is increased sensitivity to pressure, temperature, and touch. Some people experience allodynia, in which a light touch that should not hurt registers as painful.

Fatigue

Fatigue in fibromyalgia is not ordinary tiredness. People describe waking unrefreshed no matter how long they slept, and a heaviness that rest does not relieve.

Sleep problems

Difficulty falling asleep, frequent waking, and non-restorative sleep are near-universal. Restless legs syndrome and sleep apnea occur more often in people with fibromyalgia than in the general population, and both are treatable, so they are worth raising with a doctor.

Cognitive symptoms (“fibro fog”)

Many people report trouble concentrating, short-term memory lapses, difficulty finding words, and slowed thinking. Fibro fog tends to worsen during flares and when sleep is poor.

Mood symptoms

Anxiety and depression are substantially more common in people with fibromyalgia than in the general population. The relationship is complex — living with chronic pain affects mood, and mood affects pain perception — but mood symptoms are real, common, and treatable.

Other commonly reported symptoms

  • Headaches and migraines
  • Digestive symptoms, including irritable bowel syndrome
  • Tingling or numbness in the hands and feet (paresthesia)
  • Jaw and facial pain, including TMJ disorders
  • Bladder symptoms, including increased urinary urgency
  • Sensitivity to light, noise, and strong smells
  • Dizziness or balance problems
  • Dry eyes and dry mouth

What Causes Fibromyalgia Tender Points?

A doctor will try and make his diagnosis relying on his patient’s feedback. He will know that if his patient has fibromyalgia tender points and is experiencing pain and muscle aches, these symptoms can last for about three months.

Studies have found that fibromyalgia patients can even experience neuropathy. There aren’t any definite or single causes for fibromyalgia, but we have listed 6 possible causes:

Causes Fibromyalgia Tender Points

  • Candida overgrowth – Candida can overgrow and break down the intestine walls. Then it can penetrate the bloodstream and release toxic matter into the system. Generally, most people with fibromyalgia have had candida overgrowth.
  • Gluten intolerance – Can you believe that gluten intolerance is associated with over 55 diseases? It does not often manifest with digestive symptoms but more like neurological issues like fatigue, sleep disturbances, depression, cognitive impairment, behavioral issues, and pain.

  • Thyroid problems – Sometimes people with thyroid problems aren’t aware that they have problems. Yet, 90% of the time, they suffer from hypothyroidism. When checking for thyroid disorders, the doctor needs to see that the thyroid functions at the optimal range, which will relieve those problems, such as fatigue, depression, sleep disturbances, and brain fog.
  • Adrenal fatigue – Chronic stress is a major cause of adrenal fatigue because it stresses the adrenal glands. Other causes, like vitamin deficiencies, food intolerance, candida, and mercury toxicity, are the most common adrenal stressors. It is recommended that the patient supports the adrenals with adaptogenic herbs until scientific research comes up with the root cause of fibromyalgia.
  • Nutrient deficiencies – Fibromyalgia patients are very often deficient in vitamin D, magnesium, and vitamin B12. Some doctors have even claimed that when a patient boosts their magnesium levels, their conditions are reversed.
  • SIBO – small intestine bacterial overgrowth and leaky gut – When bacteria in the system get out of balance, usually as a result of a sugar-rich diet and antibiotics, you can lose your ability to digest and absorb the nutrients, particularly vitamin B12. People diagnosed with fibromyalgia or any similar chronic disease should first fix their gut because this is just a vicious cycle where everything is so closely related.

What Are the Symptoms of Fibromyalgia Tender Points?

The severity will vary from one person to the next – sometimes, the symptoms come and go. Common fibromyalgia symptoms include:

  • Fatigue – The patient experiences anything from general malaise to all-over fatigue. It feels as if the body needs recharging.
  • Cognitive function – A person can feel depressed and anxious, have a poor sense of balance, and even feel dizzy. Speech could become slurred with stuttering. Headaches that turn into migraines can be experienced, making it difficult to think clearly.
  • Sleep disorders – They also have difficulties falling asleep and then can’t stay asleep. They experience restless leg syndrome and might even suffer from sleep apnea. They often wake up due to pain and discomfort and experience their feet as ‘burning’.
  • Weakness – People have difficulty lifting their arms and using their hands – they have poor motor control. Their hips feel weak, which can cause poor balance. They might experience difficulty walking. Legs can just give way and cause them to collapse. Hands and feet experience tingling and numbness.
  • Chronic pain – The pain feels like heaviness around the neck and shoulders. The entire body feels achy and weak, particularly in the morning. Sometimes they experience chest pain, which is usually caused by costochondritis. They also experience pain in their legs, lower back, tenderness in the hands and feet, painful and swollen glands, and even pain when touched gently.
  • Depression and anxiety – Many studies are linked to fibromyalgia and depression. People with fibromyalgia are noted to have depression and anxiety up to three times more at their time of diagnosis than someone who does not have fibromyalgia.

What Is the Treatment for Fibromyalgia Tender Points?

Treatment for Fibromyalgia Tender Points
If you want to treat your fibromyalgia trigger points, you have to treat your fibromyalgia condition as a whole.

It might take a few prescriptions and doctor’s recommendations for you to change your lifestyle as well. Your doctor might prescribe these types of interventions:

  • Antidepressants
  • Anti-seizure medications
  • Non-steroidal anti-inflammatory drugs
  • Injections of steroids or other medications

The above are all different methods of treating fibromyalgia. Apart from them, it might be recommended to you that you change your lifestyle.

For instance, exercise plays a huge role in managing fibromyalgia because it deals with anxiety and depression, fatigue, and pain.

You also can deal with fibromyalgia through alternative therapists. These can be:

  • Acupuncture
  • Massage
  • Acupressure
  • Physical therapy
  • Yoga
  • Cognitive Behavioral Therapy
  • Exercise
  • Herbs and supplements

How Fibromyalgia Is Diagnosed: The ACR Criteria

There is no blood test, X-ray, or scan that can confirm fibromyalgia. Diagnosis is clinical, meaning it is based on a person’s symptoms, history, and physical examination, together with tests that rule out other explanations.

The old approach: 18 tender points

The American College of Rheumatology (ACR) published its first fibromyalgia criteria in 1990. Under those criteria, a doctor applied firm pressure to 18 specific tender points, and a person needed pain in at least 11 of them, along with widespread pain lasting at least three months.

That approach had real limitations. The examination depended on how much pressure the individual doctor applied, tenderness fluctuated from day to day, and the criteria ignored the fatigue, sleep, and cognitive symptoms that people often found most disabling. Many people with genuine fibromyalgia did not meet the 11-point threshold and went undiagnosed as a result.

The current approach: 2010 and 2016 ACR criteria

The ACR replaced the tender point examination in 2010 and refined the criteria again in 2016. The current criteria use two scored measures instead of a physical examination:

1. The Widespread Pain Index (WPI) The person indicates how many of 19 defined body areas have been painful over the past week. The score ranges from 0 to 19.

2. The Symptom Severity Scale (SSS) Three core symptoms — fatigue, waking unrefreshed, and cognitive symptoms — are each rated from 0 (no problem) to 3 (severe). Points are added for headaches, pain or cramps in the lower abdomen, and depression over the previous six months. The total ranges from 0 to 12.

A diagnosis of fibromyalgia is made when all of the following are met:

  • WPI of 7 or higher and SSS of 5 or higher, or WPI of 4 to 6 and SSS of 9 or higher
  • Generalized pain, defined as pain in at least four of five body regions
  • Symptoms present at a similar level for at least three months
  • The diagnosis is valid regardless of other diagnoses, and having fibromyalgia does not exclude other conditions

Tests used to rule out other conditions

Because fibromyalgia symptoms overlap with several other conditions, a doctor will usually order blood work not to confirm fibromyalgia but to exclude alternatives. Common tests include a complete blood count, erythrocyte sedimentation rate and C-reactive protein, thyroid function tests, vitamin D level, and, where indicated, tests for rheumatoid arthritis, lupus, or celiac disease. In fibromyalgia, these results are typically normal.

Do tender points still matter?

Tender points are no longer required for diagnosis, but they have not become irrelevant. The areas identified in 1990 still describe where many people with fibromyalgia feel the most tenderness, and some doctors still examine them as part of a broader assessment. They are now one piece of the clinical picture rather than the deciding factor.

Treatment Options

There is currently no cure for fibromyalgia. Treatment aims to reduce symptoms and improve daily function, and it works best when several approaches are combined rather than relying on any single one. What helps varies considerably from person to person, so finding an effective combination usually takes time and adjustment.

Medication

Three medications are approved by the U.S. Food and Drug Administration specifically for fibromyalgia:

  • Pregabalin (Lyrica) — an anti-seizure medication that reduces pain signaling
  • Duloxetine (Cymbalta) — a serotonin-norepinephrine reuptake inhibitor
  • Milnacipran (Savella) — also a serotonin-norepinephrine reuptake inhibitor

Doctors also prescribe several medications off-label, including low-dose amitriptyline, which is often used to improve sleep, the muscle relaxant cyclobenzaprine, and gabapentin.

Two categories are generally not recommended. Non-steroidal anti-inflammatory drugs such as ibuprofen show little benefit for fibromyalgia pain, which is consistent with the condition not being inflammatory, though they may help a coexisting condition such as osteoarthritis. Opioids are not recommended, as evidence does not support their long-term use for fibromyalgia and they carry significant risks.

All medication decisions belong with a doctor, who can weigh side effects and interactions against a person’s full medical history.

Exercise and physical therapy

Exercise has the strongest evidence base of any fibromyalgia treatment, and most clinical guidelines list it first. That can feel counterintuitive when movement hurts, but regular activity consistently improves pain, sleep, fatigue, and mood over time.

The approach that works is starting low and progressing slowly. Doing too much on a good day and paying for it afterward is one of the most common setbacks. Useful options include:

  • Low-impact aerobic activity such as walking, cycling, or swimming
  • Aquatic exercise, which is particularly well supported by research, since warm water supports body weight and eases joints
  • Strength training at light resistance, progressing gradually
  • Tai chi and yoga, which combine gentle movement with breathing and have shown benefit in trials
  • Physical therapy, where a therapist can build an individualized program, correct movement patterns, and use manual techniques

Psychological and behavioral therapies

Cognitive behavioral therapy (CBT) has good evidence in fibromyalgia. It does not treat pain as psychological in origin — it teaches practical skills for managing pain, pacing activity, challenging unhelpful thought patterns, and improving sleep. Mindfulness-based stress reduction and acceptance and commitment therapy have also shown benefit.

Sleep treatment

Because disrupted sleep both worsens and is worsened by fibromyalgia, addressing it directly is a priority. This may include cognitive behavioral therapy for insomnia (CBT-I), which is more effective long term than sleep medication, along with evaluation and treatment of sleep apnea or restless legs syndrome if either is suspected.

Complementary approaches

Some people find benefit in acupuncture, massage therapy, myofascial release, or heat therapy. Evidence is mixed and generally weaker than for exercise and CBT, but these approaches carry low risk for most people and may be worth trying alongside established treatments.

Supplements

Several nutrients and botanicals are commonly discussed in connection with fibromyalgia. It is worth being clear about what supplements can and cannot do: they are not a treatment for fibromyalgia, and no supplement has been shown to resolve the condition. They may play a supporting role within a broader plan, particularly where a deficiency exists.

  • Vitamin D — low levels are common and worth testing for. Correcting a confirmed deficiency supports normal muscle function and general wellbeing.
  • Magnesium — involved in normal muscle and nerve function. Some people with fibromyalgia report low intake.
  • Coenzyme Q10 — studied for its role in cellular energy production, with some small trials in fibromyalgia.
  • Melatonin — used to support healthy sleep patterns.
  • Omega-3 fatty acids — support general health, though evidence specific to fibromyalgia is limited.

A note on joint support formulas

Fibromyalgia is not a joint disease, and it does not damage cartilage or cause the joint changes seen in arthritis. Joint supplements therefore do not address fibromyalgia itself.

They are worth understanding for a different reason. Fibromyalgia frequently occurs alongside osteoarthritis and other joint conditions, and when both are present, the joint condition is treated on its own terms. Combination formulas such as Flexoplex Joint Support are designed with that separate goal in mind, combining ingredients commonly used to support joint comfort, flexibility, and everyday mobility. Anyone with overlapping conditions should work out with their doctor which symptoms come from which source before adding anything, since joint supplements can interact with prescription medication.

Day-to-Day Management Strategies

Beyond formal treatment, everyday habits make a substantial difference to how manageable fibromyalgia feels.

  • Pace yourself. Pacing is the single most valuable skill most people with fibromyalgia learn. The pattern of pushing hard on good days and crashing afterward — sometimes called boom and bust — keeps symptoms unstable. Breaking tasks into shorter segments with rest between them, and stopping before exhaustion rather than at it, produces more consistent capacity over time.
  • Protect your sleep. Keep consistent sleep and wake times, including weekends. Keep the bedroom cool, dark, and quiet. Limit caffeine after midday and screens in the hour before bed. Avoid long daytime naps, which make nighttime sleep harder.
  • Manage stress actively. Stress reliably worsens symptoms, so stress management is a treatment, not an optional extra. Breathing exercises, meditation, gentle movement, time outdoors, and simply having fewer commitments all help.
  • Keep moving daily. Even on difficult days, gentle movement — a short walk, light stretching — usually leaves people feeling better than complete rest does.
  • Eat regularly and reasonably. No specific fibromyalgia diet is supported by strong evidence. Regular balanced meals, adequate hydration, and limiting alcohol support steadier energy. If certain foods reliably worsen your symptoms, it is reasonable to discuss that with a doctor or dietitian rather than eliminating foods on your own.
  • Track your symptoms. A simple daily log of pain, sleep, activity, and stress helps identify triggers and gives your doctor better information than memory alone.
  • Talk to your workplace. Many people continue working with fibromyalgia, often with adjustments such as flexible hours, more frequent breaks, or ergonomic changes.
  • Build support. Chronic pain is isolating. Support groups, whether local or online, and involving family in understanding the condition both reduce that isolation. Professional mental health support is appropriate and valuable, not a last resort.

When to See a Doctor

Make an appointment if you have widespread pain lasting three months or longer, particularly alongside persistent fatigue, unrefreshing sleep, or difficulty concentrating.

Seek prompt medical attention for symptoms that are not typical of fibromyalgia, including unexplained weight loss, fever, visibly swollen or hot joints, muscle weakness that is measurable rather than a feeling of weakness, or new neurological symptoms. These suggest something other than fibromyalgia and warrant investigation.

If you already have a fibromyalgia diagnosis, contact your doctor if symptoms change noticeably in character, if a new symptom appears, or if your current treatment stops working.

Frequently Asked Questions

Q: Is fibromyalgia an autoimmune disease?

No. Fibromyalgia is not classified as an autoimmune disease, and it does not involve the immune system attacking the body’s own tissue. It is understood as a disorder of pain processing in the central nervous system. That said, fibromyalgia occurs more frequently in people who have autoimmune conditions such as lupus or rheumatoid arthritis, and a person can have both.

Q: Does fibromyalgia get worse over time?

Fibromyalgia is not a progressive condition in the way that some forms of arthritis are. It does not damage joints, muscles, or organs over time. Symptoms fluctuate, with flares and quieter periods, and many people find their symptoms become more manageable as they learn what helps.

Q: Is there a blood test for fibromyalgia?

No. There is no laboratory test that confirms fibromyalgia. Blood tests are used to rule out other conditions with similar symptoms, such as thyroid disorders, rheumatoid arthritis, or vitamin D deficiency. In fibromyalgia, those tests are typically normal.

Q: Can men get fibromyalgia?

Yes. Fibromyalgia is diagnosed more often in women, but men develop it too. Researchers increasingly believe men are underdiagnosed, partly because the condition has historically been framed as affecting women.

Q: Is fibromyalgia the same as chronic fatigue syndrome?

No, though they share several symptoms and can occur together. In fibromyalgia, widespread pain is the defining symptom. In myalgic encephalomyelitis/chronic fatigue syndrome, the defining feature is post-exertional malaise, a marked worsening of symptoms after physical or mental exertion.

Q: Does exercise make fibromyalgia worse?

Starting too intensely can trigger a flare, which is why so many people conclude that exercise is not for them. Started gently and increased gradually, exercise has the strongest evidence of any fibromyalgia treatment for improving pain, sleep, and fatigue over time. Working with a physical therapist to set the starting point makes this much easier.

Q: How long does it take to get a fibromyalgia diagnosis?

It often takes considerable time, in many cases two years or more, because the symptoms overlap with other conditions and there is no confirmatory test. Bringing a written symptom history to appointments, including when symptoms began and how they affect daily life, can help.

Q: Can fibromyalgia go into remission?

Some people experience long periods with few or mild symptoms. Fibromyalgia is generally considered a long-term condition rather than one that resolves permanently, but symptom severity varies widely, and many people reach a point where symptoms no longer dominate daily life.

Conclusion

The primary symptoms of fibromyalgia are widespread pain – like a constant dull ache that can last for three months.

Not all fibromyalgia cases experience the same pain. Some people experience mild to moderate amounts of fibromyalgia and can live a normal life – if they undergo treatment.

People with severe fibromyalgia pain might be prevented from doing a job properly or even having a social life.

Things like anxiety, changes in the weather, fatigue, hormonal changes, infections, and sleep problems can make fibromyalgia worse.

Today, there are updated guidelines to diagnose fibromyalgia. The research found that many patients who did have fibromyalgia didn’t meet the tender point’s criteria. Doctors realized many patients were being underdiagnosed.

Lifestyle modifications are critical when it comes to managing fibromyalgia symptoms, especially exercise. Exercise can help address many issues related to fibromyalgia (another name is Myalgic Encephalomyelitis or chronic fatigue syndrome).

References

  • https://pmc.ncbi.nlm.nih.gov/articles/PMC8068842/
  • https://pmc.ncbi.nlm.nih.gov/articles/PMC7113112/
  • https://pmc.ncbi.nlm.nih.gov/articles/PMC4997656/
  • https://www.ncbi.nlm.nih.gov/books/NBK532931/