Common symptoms of pain disorder are: negative or distorted cognition, such as feelings of despair or hopelessness; inactivity and passivity, in some cases disability; increased pain, sometimes requiring clinical treatment; sleep disturbance and fatigue; disruption of social relationships; depression and/or anxiety. Acute conditions last less than six months while chronic pain disorder lasts six or more months.

There is no neurological or physiological basis for the pain. Pain is reported as more distressing than it should be if there was a physical explanation. People who suffer from this disorder may begin to abuse medication.

The DSM-IV-TR specifies three coded subdiagnoses: pain disorder associated with psychological factors, pain disorder associated with both psychological factors and a general medical condition and pain disorder associated with a general medical condition (although the latter subtype is not considered a mental disorder and is coded separately within the DSM-IV-TR). Conditions such as dyspareunia, somatization disorder, conversion disorder, or mood disorders can eliminate pain disorder as a diagnosis. Diagnosis depends on the ability of physicians to explain the symptoms and on psychological influences.

Psychogenic pain, also called psychalgia, is physical pain that is caused, increased, or prolonged by mental, emotional, or behavioral factors.

Headache, back pain, or stomach pain are some of the most common types of psychogenic pain. It may occur, rarely, in persons with a mental disorder, but more commonly it accompanies or is induced by social rejection, broken heart, grief, lovesickness, or other such emotional events.

Sufferers are often stigmatized, because both medical professionals and the general public tend to think that pain from psychological source is not "real". However, specialists consider that it is no less actual or hurtful than pain from other sources.

The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, "or described in terms of such damage"" (emphasis added). In the note accompanying that definition, the following can be found about pain that happens for psychological reasons:

Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain.

Medicine refers also to psychogenic pain or psychalgia as a form of chronic pain under the name of "persistent somatoform pain disorder" or "functional pain syndrome". Causes may be linked to stress, unexpressed emotional conflicts, psychosocial problems, or various mental disorders. Some specialists believe that psychogenic chronic pain exists as a protective distraction to keep dangerous repressed emotions such as anger or rage unconscious.

It remains controversial, however, that chronic pain might arise purely from emotional causes. Treatment may include psychotherapy, antidepressants, analgesics, and other remedies that are used for chronic pain in general.

Functional somatic syndrome is characterized by ambiguous, non-specific symptoms that appear in otherwise-healthy populations. Overlap exists in different syndromes, including gastrointestinal issues, pain, fatigue, cognitive difficulties, and sleep difficulties. Some have proposed to group symptoms into clusters or into one general functional somatic disorder given the finding of correlations between symptoms and underlying etiologies.

Functional somatic syndrome is a term used to refer to physical symptoms that are poorly explained. It encompass disorders such as chronic fatigue syndrome, fibromyalgia, chronic widespread pain, temporomandibular disorder, irritable bowel syndrome, lower back pain, tension headache, atypical face pain, non-cardiac chest pain, insomnia, palpitation, dyspepsia, and dizziness. General overlap exists between this term, somatization, and somatoform.

Irritable Bowel Syndrome (IBS),

Fibromyalgia (FMS),

Chronic Fatigue Syndrome (CFS),

Chronic Pelvic Pain (CPP),

Interstitial Cystitis (IC),

Temporomandibular Joint Pain (TMJ), Functional Neurological Symptom Disorder (FNsD),

Non-Cardiac Chest Pain (NCCP),

Post-Traumatic Stress Disorder (PTSD),

Dysuria (Pain On Urination),

and Multiple Chemical Sensitivity

Atypical facial pain (AFP) is a type of chronic facial pain which does not fulfill any other diagnosis. There is no consensus as to a globally accepted definition, and there is even controversy as to whether the term should be continued to be used. Both the International Headache Society (IHS) and the International Association for the Study of Pain (IASP) have adopted the term persistent idiopathic facial pain (PIFP) to replace AFP. In the 2nd Edition of the International Classification of Headache Disorders (ICHD-2), PIFP is defined as "persistent facial pain that does not have the characteristics of the cranial neuralgias [...] and is not attributed to another disorder." However, the term AFP continues to be used by the World Health Organization's 10th revision of the International Statistical Classification of Diseases and Related Health Problems and remains in general use by clinicians to refer to chronic facial pain that does not meet any diagnostic criteria and does not respond to most treatments.

The main features of AFP are: no objective signs, negative results with all investigations/ tests, no obvious explanation for the cause of the pain, and a poor response to attempted treatments. AFP has been described variably as a medically unexplained symptom, a diagnosis of exclusion, a psychogenic cause of pain (e.g. a manifestation of somatoform disorder), and as a neuropathy. AFP is usually burning and continuous in nature, and may last for many years. Depression and anxiety are often associated with AFP, which are either described as a contributing cause of the pain, or the emotional consequences of suffering with unrelieved, chronic pain. For unknown reasons, AFP is significantly more common in middle aged or elderly people, and in females.

Atypical odontalgia (AO) is very similar in many respects to AFP, with some sources treating them as the same entity, and others describing the former as a sub-type of AFP. Generally, the term AO may be used where the pain is confined to the teeth or gums, and AFP when the pain involves other parts of the face. As with AFP, there is a similar lack of standardization of terms and no consensus regarding a globally accepted definition surrounding AO. Generally definitions of AO state that it is pain with no demonstrable cause which is perceived to be coming from a tooth or multiple teeth, and is not relieved by standard treatments to alleviate dental pain.

Depending upon the exact presentation of atypical facial pain and atypical odontalgia, it could be considered as craniofacial pain or orofacial pain. It has been suggested that, in truth, AFP and AO are umbrella terms for a heterogenous group of misdiagnosed or not yet fully understood conditions, and they are unlikely to each represent a single, discrete condition.

A functional disorder is a medical condition that impairs the normal function of a bodily process, but where every part of the body looks completely normal under examination, dissection or even under a microscope. This stands in contrast to a structural disorder (in which some part of the body can be seen to be abnormal) or a psychosomatic disorder (in which symptoms are caused by psychological or psychiatric illness). Definitions vary somewhat between fields of medicine.

Generally, the mechanism that causes a functional disorder is unknown, poorly understood, or occasionally unimportant for treatment purposes. The brain or nerves are often believed to be involved. It is common that a person with one functional disorder will have others.

While not often volunteered as a complaint, upon questioning, it has been found that pain is a common co-morbidity. Pains may include joint pain, muscle aches, headaches and stomachaches. Clinical experience has shown that after the OC and other psychiatric symptoms have improved, some children report pain for the first time. When widespread pain is present, patients often report other forms of sensory amplification and poor sleep. Physical exam may reveal areas of tenderness to palpation in the classic distribution for fibromyalgia. Patients who report both pain and stiffness upon awakening or after prolonged stationary positions should be assessed for arthritis. A small fraction of patients with PANS have been afflicted by an arthritis condition (inflammatory back pain, reactive arthritis, psoriatic arthritis, and juvenile idiopathic arthritis). Reactive arthritis (most commonly in the ankles, knees, and hips) has been reported before PANS onset. Involvement of the pediatrician, pediatric rheumatologist, pain specialist, occupational therapist, and physical therapist may help the course of the illness, alleviate pain and likely, improve emotional functioning.

According to the 2017 "Survey of Pediatric Acute-Onset Neuropsychiatric Syndrome Characteristics and Course" these symptoms may occur in PANS patients:

AFP has also been described as a medically unexplained symptom, which are thought by some to be largely psychogenic in nature. However, true psychogenic pain is considered to be rare. Some sources have assigned or categorized AFP as a psychosomatic manifestation of somatoform disorder, as defined in the Diagnostic and Statistical Manual of the American Psychiatric Association. Distinction should be made between somatoform disorder, where affected individuals are not inventing the symptom for some benefit, and other conditions like factitious disorder or malingering.

Recent evidence in chronic facial pain research appear to suggest that a proportion of individuals who have been diagnosed with AFP have neuropathic pain,

AFP is described as one of the 4 recognizable symptom complexes of chronic facial pain, along with burning mouth syndrome, temporomandibular joint dysfunction (TMD) and atypical odontalgia. However, there is a degree of overlap between the features of these diagnoses, e.g. between AFP and TMD and burning mouth syndrome.

Atypical odontalgia is similar in nature to AFP, but the latter term generally is used where the pain is confined to the teeth or gums, and AFP when the pain involves other parts of the face. Other sources use atypical odontalgia and AFP as synonyms, or describe atypical odontalgia as a sub-type, variant, or intra-oral equivalent of AFP. Sometimes "phantom tooth pain" is listed as a synonym for AO, and sometimes it is defined as toothache which persists after a tooth has been extracted. It has been suggested that it is likely that these terms do not represent a single, discrete condition, but rather a collection of misdiagnosed and as yet unidentified causes. This pain is often similar to pain from organic dental disease such as periapical periodontitis, or pulpitis (toothache), but unlike normal dental pain, it is not relieved in the long term by dental treatments such as endodontic therapy (root canal treatment) or tooth extraction, and it may even be worsened, return soon after, or simply migrate to other areas in the mouth following dental treatment.

ATN pain can be described as heavy, aching, stabbing, and burning. Some sufferers have a constant migraine-like headache. Others may experience intense pain in one or in all three trigeminal nerve branches, affecting teeth, ears, sinuses, cheeks, forehead, upper and lower jaws, behind the eyes, and scalp. In addition, those with ATN may also experience the shocks or stabs found in type 1 TN.

Many TN and ATN patients have pain that is "triggered" by light touch on shifting trigger zones. ATN pain tends to worsen with talking, smiling, chewing, or in response to sensations such as a cool breeze. The pain from ATN is often continuous, and periods of remission are rare. Both TN and ATN can be bilateral, though the character of pain is usually different on the two sides at any one time.

Dysesthesia can generally be described as a class of neurological disorders. It can be further classified depending on where it manifests in the body, and by the type of sensation that it provokes.

Cutaneous dysesthesia is characterized by discomfort or pain from touch to the skin by normal stimuli, including clothing. The unpleasantness can range from a mild tingling to blunt, incapacitating pain.

Scalp dysesthesia is characterized by pain or burning sensations on or under the surface of the cranial skin. Scalp dysesthesia may also present as excessive itching of the scalp.

Occlusal dysesthesia, or "phantom bite", is characterized by the feeling that the bite is "out of place" (occlusal dystopia) despite any apparent damage or instability to dental or oromaxillofacial structures or tissue. Phantom bite often presents in patients that have undergone otherwise routine dental procedures. Short of compassionate counseling, evidence for effective treatment regimes is lacking.

In the DSM-5 the disorder has been renamed somatic symptom disorder (SSD), and includes SSD with predominantly somatic complaints (previously referred to as somatization disorder), and SSD with pain features (previously known as pain disorder).

The defining symptoms of fibromyalgia are chronic widespread pain, fatigue, sleep disturbance, and heightened pain in response to tactile pressure (allodynia). Other symptoms may include tingling of the skin (paresthesias), prolonged muscle spasms, weakness in the limbs, nerve pain, muscle twitching, palpitations, and functional bowel disturbances.

Many people experience cognitive dysfunction (known as "fibrofog"), which may be characterized by impaired concentration, problems with short and long-term memory, short-term memory consolidation, impaired speed of performance, inability to multi-task, cognitive overload, and diminished attention span. Fibromyalgia is often associated with anxiety and depressive symptoms.

Other symptoms often attributed to fibromyalgia that may be due to a comorbid disorder include myofascial pain syndrome, also referred to as chronic myofascial pain, diffuse non-dermatomal paresthesias, functional bowel disturbances and irritable bowel syndrome, genitourinary symptoms and interstitial cystitis, dermatological disorders, headaches, myoclonic twitches, and symptomatic hypoglycemia. Although fibromyalgia is classified based on the presence of chronic widespread pain, pain may also be localized in areas such as the shoulders, neck, low back, hips, or other areas. Many sufferers also experience varying degrees of myofascial pain and have high rates of comorbid temporomandibular joint dysfunction. 20–30% of people with rheumatoid arthritis and systemic lupus erythematosus may also have fibromyalgia.

ATN is usually attributed to inflammation or demyelination, with increased sensitivity of the trigeminal nerve. These effects are believed to be caused by infection, demyelinating diseases, or compression of the trigeminal nerve (by an impinging vein or artery, a tumor, or arteriovenous malformation) and are often confused with dental problems. An interesting aspect is that this form affects both men and women equally and can occur at any age, unlike typical trigeminal neuralgia, which is seen most commonly in women. Though TN and ATN most often present in the fifth decade, cases have been documented as early as infancy.

For people with this disorder, cognition and sensation are otherwise normal; for instance, patients can still feel discriminative touch (though not always temperature), and there are no detectable physical abnormalities.

Because children with the disorder cannot feel pain, they may not respond to problems, thus being at a higher risk of more severe diseases. Children with this condition often suffer oral cavity damage both in and around the oral cavity (such as having bitten off the tip of their tongue) or fractures to bones. Unnoticed infections and corneal damage due to foreign objects in the eye are also seen.

There are generally two types of non-response exhibited:

- Insensitivity to pain means that the painful stimulus is not even perceived: a patient cannot describe the intensity or type of pain.

- Indifference to pain means that the patient can perceive the stimulus, but lacks an appropriate response: they do not flinch or withdraw when exposed to pain.

Although dysesthesia is similar to phantom limb syndrome, they should not be confused. In phantom limb, the sensation is present in an amputated or absent limb, while dysesthesia refers to discomfort or pain in a tissue that has not been removed or amputated. The dysesthetic tissue may also not be part of a limb, but part of the body, such as the abdomen. The majority of individuals with both phantom limb and dysesthesia experience painful sensations.

Phantom pain refers to dysesthetic feelings in individuals who are paralyzed or who were born without limbs. It is caused by the improper innervation of the missing limbs by the nerves that would normally innervate the limb. Dysesthesia is caused by damage to the nerves themselves, rather than by an innervation of absent tissue.

Dysesthesia should not be confused with anesthesia or hypoesthesia, which refer to a loss of sensation, or paresthesia which refers to a distorted sensation. Dysesthesia is distinct in that it can, but not necessarily, refer to spontaneous sensations in the absence of stimuli. In the case of an evoked dysesthetic sensation, such as by the touch of clothing, the sensation is characterized not simply by an exaggeration of the feeling, but rather by a completely inappropriate sensation such as burning.

Fibromyalgia is classed as a disorder of pain processing due to abnormalities in how pain signals are processed in the central nervous system. The American College of Rheumatology classifies fibromyalgia as being a functional somatic syndrome. The expert committee of the European League Against Rheumatism classifies fibromyalgia as a neurobiological disorder and as a result exclusively give pharmacotherapy their highest level of support. The International Classification of Diseases (ICD-10) lists fibromyalgia as a diagnosable disease under "Diseases of the musculoskeletal system and connective tissue," under the code M79-7, and states that fibromyalgia syndrome should be classified as a functional somatic syndrome rather than a mental disorder. Although mental disorders and some physical disorders commonly are co-morbid with fibromyalgia – especially anxiety, depression, irritable bowel syndrome, and chronic fatigue syndrome – the ICD states that these should be diagnosed separately.

Differences in psychological and autonomic nervous system profiles among affected individuals may indicate the existence of fibromyalgia subtypes. A 2007 review divides individuals with fibromyalgia into four groups as well as "mixed types":

1. "extreme sensitivity to pain but no associated psychiatric conditions" (may respond to medications that block the 5-HT3 receptor)

2. "fibromyalgia and comorbid, pain-related depression" (may respond to antidepressants)

3. "depression with concomitant fibromyalgia syndrome" (may respond to antidepressants)

4. "fibromyalgia due to somatization" (may respond to psychotherapy)

Somatization disorder (also Briquet's syndrome) is a mental disorder characterized by recurring, multiple, and current, clinically significant complaints about somatic symptoms, although it is no longer considered a clinical diagnosis. It was recognized in the DSM-IV-TR classification system, but in the latest version DSM-5, it was combined with undifferentiated somatoform disorder to become "somatic symptom disorder", a diagnosis which no longer requires a specific number of somatic symptoms. ICD-10, the latest version of the International Statistical Classification of Diseases and Related Health Problems, still includes somatization syndrome.

The International Headache Society classifies ophthalmodynia periodica as a primary stabbing headache.

Somatic symptom disorders are a group of disorders, all of which fit the definition of physical symptoms similar to those observed in physical disease or injury for which there is no identifiable physical cause. As such, they are a diagnosis of exclusion. Somatic symptoms may be generalized in four major medical categories: neurological, cardiac, pain, and gastrointestinal somatic symptoms.

The following diagnostic criteria are given for ophthalmodynia periodica:

1. Head pain occurring as a single stab or a series of stabs

2. Solely felt in the areas surrounding the eyes and temples

3. Pain lasting only a few seconds with irregular frequency

4. No additional symptoms

5. "Not attributed to another disorder"

The headaches can vary greatly in their clinical presentation and duration.

Quality of the headache has been described as dull and/or pressure-like sensation, and throbbing and/or pulsating sensation. The pain is usually on both sides of the head (in 88–93% of people with NDPH), but may be unilateral, and may be localized to any head region. The pain can fluctuate in intensity and duration, is daily, and lasts more than 3 months.

There may be accompanying photophobia, phonophobia, lightheadedness or mild nausea. Co-morbidity with mood disorders has been reported in a subset of patients.

Cranial autonomic nervous symptoms occur with painful exacerbations in 21%, and cutaneous allodynia may be present in 26%.

In 2002, Li and Rozen conducted a study of 56 patients at the Jefferson Headache Center in Philadelphia and published the following results:

- 82% of patients were able to pinpoint the exact day their headache started.

- 30% of the patients, the onset of the headache occurred in correlation with an infection or flu-like illness.

- 38% of the patients had a prior personal history of headache.

- 29% of the patients had a family history of headache.

- 68% reported nausea.

- 66% reported photophobia.

- 61% reported phonophobia.

- 55% reported lightheadedness.

Imaging and laboratory testing were unremarkable except for an unusually high number of patients who tested positive for a past Epstein-Barr virus infection.

It most often occurs in the middle of the night and lasts from seconds to minutes, an indicator for the differential diagnosis of levator ani syndrome, which presents as pain and aching lasting twenty minutes or longer. In a study published in 2007 involving 1809 patients, the attacks occurred in the daytime (33 per cent) as well as at night (33 per cent) and the average number of attacks was 13. Onset can be in childhood; however, in multiple studies the average age of onset was 45. Many studies showed that women are affected more commonly than men. This can be at least partly explained by men's reluctance to seek medical advice concerning such a delicate case as rectal pain.

During an episode, the patient feels spasm-like, sometimes excruciating, pain in the anus, often misinterpreted as a need to defecate. The pain must arise de novo, that is in absence of clear cause. As such, pain associated with penetrative anal intercourse, trauma or rectal foreign body insertion preclude a diagnosis of proctalgia fugax. Simultaneous stimulation of the local autonomic system can cause erection in males. In some people, twinges sometimes occur shortly after orgasm. Because of the high incidence of internal anal sphincter thickening with the disorder, it is thought to be a disorder of the internal anal sphincter or that it is a neuralgia of pudendal nerves. It is recurrent and there is also no known cure. However, some studies show effective use of botulinum toxin, pudendal nerve block, and calcium channel blockers. It is not known to be linked to any disease process and data on the number of people afflicted vary, but prevalence may be as high as 8–18%. It is thought that only 17–20% of sufferers consult a physician, so obtaining accurate data on occurrence presents a challenge.

The pain episode subsides by itself as the spasm disappears on its own, but may reoccur.