The prognosis is best when identified early and treated aggressively. In these cases NMS is not usually fatal. In previous studies the mortality rates from NMS have ranged from 20%–38%; however, in the last two decades, mortality rates have fallen below 10% due to early recognition and improved management. Re-introduction to the drug that originally caused NMS to develop may also trigger a recurrence, although in most cases it does not.

Memory impairment is a consistent feature of recovery from NMS, and usually temporary, though in some cases, may become persistent.

Differentiating NMS from other neurological disorders can be very difficult. It requires expert judgement to separate symptoms of NMS from other diseases. Some of the most commonly mistaken diseases are encephalitis, toxic encephalopathy, status epilepticus, heat stroke, and malignant hyperthermia. Due to the comparative rarity of NMS, it is often overlooked and immediate treatment for the syndrome is delayed. Drugs such as cocaine and amphetamine may also produce similar symptoms.

The differential diagnosis is similar to that of hyperthermia, and includes serotonin syndrome. Features which distinguish NMS from serotonin syndrome include bradykinesia, muscle rigidity, and a high white blood cell count.

Patients who develop PSH after traumatic injury have longer hospitalization and longer durations in intensive care in cases where ICU treatment is necessary. Patients often are more vulnerable to infections and spend longer times on ventilators, which can lead to an increased risk of various lung diseases. PSH does not affect mortality rate, but it increases the amount of time it takes a patient to recover from injury, compared to patients with similar injuries who do not develop PSH episodes. It often takes patients who develop PSH longer to reach similar levels of the brain activity seen in patients who do not develop PSH, although PSH patients do eventually reach these same levels.

Diagnosing PSH can be very difficult due to the lack of common terminology in circulation and a lack of diagnostic criteria. Different systems for diagnosis have been proposed, but a universal system has not been embraced. One example of a proposed system of diagnosis requires observation confirmation for four of the six following symptoms: fever greater than 38.3 degrees Celsius, tachycardia classified as a heart rate of 120 bpm or higher, hypertension classified as a systolic pressure higher than 160 mmHg or a pulse pressure higher than 80 mmHg, tachypnea classified as respiration rate higher than 30 breaths per minute, excess sweating, and severe dystonia. Ruling out other diseases or syndromes that show similar symptoms is imperative to diagnosis as well. Sepsis, encephalitis, neuroleptic malignant syndrome,

malignant hyperthermia, lethal catatonia, spinal cord injury (not associated with PSH), seizures, and hydrocephalus (this can be associated with PSH) are examples of diagnoses that should be considered due to the manifestation of similar symptoms before confirming a diagnosis of PSH. PSH has no simple radiological features that can be observed or detected on a scan.

Genetic testing is being performed in a limited fashion to determine susceptibility to MH. In people with a family history of MH, analysis for "RYR1" mutations may be useful.

The main candidates for testing are those with a close relative who has suffered an episode of MH or have been shown to be susceptible. The standard procedure is the "caffeine-halothane contracture test", CHCT. A muscle biopsy is carried out at an approved research center, under local anesthesia. The fresh biopsy is bathed in solutions containing caffeine or halothane and observed for contraction; under good conditions, the sensitivity is 97% and the specificity 78%. Negative biopsies are "not" definitive, so any patient who is suspected of MH by their medical history or that of blood relatives is generally treated with non-triggering anesthetics, even if the biopsy was negative. Some researchers advocate the use of the "calcium-induced calcium release" test in addition to the CHCT to make the test more specific.

Less invasive diagnostic techniques have been proposed. Intramuscular injection of halothane 6 vol% has been shown to result in higher than normal increases in local among patients with known malignant hyperthermia susceptibility. The sensitivity was 100% and specificity was 75%. For patients at similar risk to those in this study, this leads to a positive predictive value of 80% and negative predictive value of 100%. This method may provide a suitable alternative to more invasive techniques.

A 2002 study examined another possible metabolic test. In this test, intramuscular injection of caffeine was followed by local measurement of the ; those with known MH susceptibility had a significantly higher (63 versus 44 mmHg). The authors propose larger studies to assess the test's suitability for determining MH risk.

Tardive dysphrenia is characterized by a worsening of psychiatric symptoms that can be directly traced to the administration of antipsychotic medication.

Six symptoms are considered when diagnosing tardive dysphrenia:

A) The patient shows:

B) The symptoms are present for a full four weeks (full two weeks if successfully treated by immediate reinstitution or augmentation with a more potent drug and/or the rising of the previous drug) and contain any of these patterns:

C) Criteria A & B signs and symptoms emerge progressively with the administration of an oral antipsychotic drug or during the four-weeks period that follows its withdrawal (8 weeks for dépôt formulations).

D) There has been any exposure to a typical and/or atypical antipsychotic drug for at least three full months (full 12 weeks), or 1 full month (full 4 weeks) if the patient is sixty years old or older.

E) The clinical signs and symptoms cannot be attributed to another psychiatric condition, neurological condition, somatic illness, or severe stress. Also, exposure to other psychosis-inducing medicines must be excluded.

F) The signs and symptoms could not be better explained by an eventual previous psychiatric/neurological condition unfavorable natural evolution (i.e., Primary Refractory or poor prognosis Schizophrenia; severe Acute Mania; Dementia with Psychotic Symptoms) or by Neuroleptic Dysphoria.

There is no laboratory test for serotonin syndrome. Therefore, diagnosis is by symptom observation and investigation of the patient's history. Several diagnostic criteria have been proposed. The first rigorously evaluated criteria were introduced in 1991 by Harvey Sternbach, a professor of psychiatry at UCLA. Researchers in Australia later developed the Hunter Toxicity Criteria Decision Rules, which have better sensitivity and specificity, 84% and 97%, respectively, when compared with the gold standard of diagnosis by a medical toxicologist. As of 2007, Sternbach's criteria were still the most commonly used.

The most important symptoms for diagnosing serotonin syndrome are tremor, extreme aggressiveness, akathisia, or clonus (spontaneous, inducible and ocular). Physical examination of the patient should include assessment of deep-tendon reflexes and muscle rigidity, the dryness of the mucosa of the mouth, the size and reactivity of the pupils, the intensity of bowel sounds, skin color, and the presence or absence of sweating. The patient's history also plays an important role in diagnosis, investigations should include inquiries about the use of prescription and over-the-counter drugs, illicit substances, and dietary supplements, as all these agents have been implicated in the development of serotonin syndrome. To fulfill the Hunter Criteria, a patient must have taken a serotonergic agent and meet one of the following conditions:

- Spontaneous clonus, or

- Inducible clonus plus agitation or diaphoresis, or

- Ocular clonus plus agitation or diaphoresis, or

- Tremor plus hyperreflexia, or

- Hypertonism plus temperature > plus ocular clonus or inducible clonus

Upon the discontinuation of serotonergic drugs, most cases of serotonin syndrome resolve within 24 hours, although in some cases delirium may persist for a number of days. Symptoms typically persist for a longer time frame in patients taking drugs which have a long elimination half-life, active metabolites, or a protracted duration of action.

Cases have reported muscle pain and weakness persisting for months, and antidepressant discontinuation may contribute to ongoing features. Following appropriate medical management, serotonin syndrome is generally associated with a favorable prognosis.

As with other neuroleptic-induced tardive syndromes, there is no definite treatment for tardive dysphrenia. The continuing to take the drug or changing the dosage of the atypical antipsychotic drug in use, or augmenting it with a typical antipsychotic, can alleviate symptoms temporarily. However, these solutions carry the risk of worsening or perpetuating the iatrogenesis in the long term.

Some patients could gradually benefit from changing to a dopamine D2 receptor partial agonist agent like clozapine. These drugs do not induce up-regulation, instead acting as a prophylactic.

Fink and Taylor developed a catatonia rating scale to identify the syndrome. A diagnosis is verified by a benzodiazepine or barbiturate test. The diagnosis is validated by the quick response to either benzodiazepines or electroconvulsive therapy (ECT). While proven useful in the past, barbiturates are no longer commonly used in psychiatry; thus the option of either benzodiazepines or ECT.

There are two lines of treatment for Pisa syndrome. The first line entails discontinuation or reduction in dose of the antipsychotic drug(s). The second line of treatment is an anticholinergic medication. A pharmacological therapy for Pisa syndrome caused by prolonged use of antipsychotic drugs has not been established yet.

According to the DSM-5, "Catatonia Associated with Another Mental Disorder (Catatonia Specifier)" (code 293.89 [F06.1]) is diagnosed if the clinical picture is dominated by at least three of the following:

- stupor (i.e., no psychomotor activity; not actively relating to environment)

- catalepsy (i.e., passive induction of a posture held against gravity)

- waxy flexibility (i.e., allow positioning by examiner and maintain position)

- mutism (i.e., no, or very little, verbal response [exclude if known aphasia])

- negativism (i.e., opposition or no response to instructions or external stimuli)

- posturing (i.e., spontaneous and active maintenance of a posture against gravity)

- mannerisms (i.e., odd, circumstantial caricature of normal actions)

- stereotypy (i.e., repetitive, abnormally frequent, non-goal-directed movements)

- agitation, not influenced by external stimuli

- grimacing (i.e. making a grimace like children)

- echolalia (i.e., mimicking another's speech)

- echopraxia (i.e., mimicking another's movements)

Other disorders (used additional code 293.89 [F06.1] to indicate the presence of the comorbid catatonia):

- Catatonia associated with autism spectrum disorder.

- Catatonia associated with schizophrenia spectrum and other psychotic disorders.

- Catatonia associated with brief psychotic disorder

- Catatonia associated with schizophreniform disorder

- Catatonia associated with schizoaffective disorder

- Catatonia associated with substance-induced psychotic disorder

- Catatonia associated with bipolar and related disorders.

- Catatonia associated with major depressive disorder

- Catatonic disorder due to another medical condition.

If catatonic symptoms are present but they are don't form the catatonic syndrome, a medication-induced or substance-induced aetiology should first be considered.

Anticholinergic drugs have been reported to be extremely effective in 40% of the patients with the Pisa syndrome. Patients with Pisa syndrome that is resistant to anticholinergic drugs is mostly resolved by the reduction of the administration of the antipsychotic drugs as previously mentioned. While the specific pathology underlying idiopathic Pisa syndrome is unknown, the administration of anticholinergic drugs has provided resolution in known cases.

Published epidemiological data for akathisia are mostly limited to treatment periods preceding the arrival of second-generation antipsychotics. Sachdev (1995) reported an incidence rate of acute akathisia of 31% for 100 patients treated for 2 weeks with antipsychotic medications. Sachdev (1995) reported a prevalence range from 0.1% to 41%. In all likelihood, rates of prevalence are lower for current treatment as second-generation antipsychotics carry a lower risk of akathisia.

SPS is diagnosed by evaluating clinical findings and excluding other conditions. There is no specific laboratory test that confirms its presence. Underdiagnosis and misdiagnosis are common.

The presence of antibodies against GAD is the best indication of the condition that can be detected by blood and cerebrospinal fluid (CSF) testing. Anti-GAD65 is found in about 80 percent of SPS patients. Anti-thyroid, anti-intrinsic factor, anti-nuclear, anti-RNP, and anti-gliadin are also often present in blood tests. Electromyography (EMG) demonstrates involuntary motor unit firing in SPS patients. EMG can confirm the diagnosis by noting spasms in distant muscles as a result of subnoxious stimulation of cutaneous or mixed nerves. Responsiveness to diazepam helps confirm that the patient is suffering from SPS, as this decreases stiffness and motor unit potential firing.

The same general criteria are used to diagnose paraneoplastic SPS as the normal form of the condition. Once SPS is diagnosed, poor response to conventional therapies and the presence of cancer indicate that it may be paraneoplastic. CT scans are indicated for SPS patients who respond poorly to therapy to determine if this is the case.

A variety of conditions have similar symptoms to SPS, including myelopathies, dystonias, spinocerebellar degenerations, primary lateral sclerosis, neuromyotonia, and some psychogenic disorders. Tetanus, neuroleptic malignant syndrome, malignant hyperpyrexia, chronic spinal interneuronitis, serotonin syndrome, Multiple sclerosis, Parkinson's disease, and Isaacs syndrome should also be excluded.

Patients' fears and phobias often incorrectly lead doctors to think their symptoms are psychogenic, and they are sometimes suspected of malingering. It takes an average of six years after the onset of symptoms before the disease is diagnosed.

Prevention of tardive dyskinesia is achieved by using the lowest effective dose of a neuroleptic for the shortest time. However, with diseases of chronic psychosis such as schizophrenia, this strategy must be balanced with the fact that increased dosages of neuroleptics are more beneficial in preventing recurrence of psychosis. If tardive dyskinesia is diagnosed, the causative drug should be discontinued. Tardive dyskinesia may persist after withdrawal of the drug for months, years or even permanently. Some studies suggest that physicians should consider using atypical antipsychotics as a substitute to typical antipsychotics for patients requiring medication. These agents are associated with fewer neuromotor side effects and a lower risk of developing tardive dyskinesia.

Recent studies have tested the use of melatonin, high dosage vitamins, and different antioxidants in concurrence with antipsychotic drugs (often used to treat schizophrenia) as a way of preventing and treating tardive dyskinesia. Although further research is needed, studies reported a much lower percentage of individuals developing tardive dyskinesia than the current prevalence rate for those taking antipsychotic drugs.

The presence and severity of akathisia can be measured using the Barnes Akathisia Scale, which assesses both objective and subjective criteria. Precise assessment of akathisia is problematic, as it is difficult to differentiate from a multitude of disorders with similar symptoms. In a study of movement disorders induced by neuroleptics, akathisia was found in only 26% of patients originally diagnosed with akathisia. The primary distinguishing features of akathisia in comparison with other syndromes are primarily subjective characteristics, such as the feeling of inner restlessness. Akathisia can commonly be mistaken for agitation secondary to psychotic symptoms or mood disorder, antipsychotic dysphoria, restless legs syndrome (RLS), anxiety, insomnia, drug withdrawal states, tardive dyskinesia, or other neurological and medical conditions.

Additionally, the controversial diagnosis of "pseudoakathisia" is given, as noted by Mark J. Garcia. In his article discussing akathisia among adults with severe and profound intellectual disability, he describes pseudoakathisia as "comprising all the symptoms of abnormal movements seen with akathisia, but without a sense of restlessness".

When ambient temperature is excessive, humans and many animals cool themselves below ambient by evaporative cooling of sweat (or other aqueous liquid; saliva in dogs, for example); this helps prevent potentially fatal hyperthermia. The effectiveness of evaporative cooling depends upon humidity. Wet-bulb temperature, which takes humidity into account, or more complex calculated quantities such as wet-bulb globe temperature (WBGT), which also takes solar radiation into account, give useful indications of the degree of heat stress and are used by several agencies as the basis for heat-stress prevention guidelines. (Wet-bulb temperature is essentially the lowest skin temperature attainable by evaporative cooling at a given ambient temperature and humidity.)

A sustained wet-bulb temperature exceeding 35 °C is likely to be fatal even to fit and healthy people unclothed in the shade next to a fan; at this temperature, environmental heat gain instead of loss occurs. , wet-bulb temperatures only very rarely exceeded 30 °C anywhere, although significant global warming may change this.

In cases of heat stress caused by physical exertion, hot environments, or protective equipment, prevention or mitigation by frequent rest breaks, careful hydration, and monitoring body temperature should be attempted. However, in situations demanding one is exposed to a hot environment for a prolonged period or must wear protective equipment, a personal cooling system is required as a matter of health and safety. There is a variety of active or passive personal cooling systems; these can be categorized by their power sources and whether they are person- or vehicle-mounted.

Because of the broad variety of operating conditions, these devices must meet specific requirements concerning their rate and duration of cooling, their power source, and their adherence to health and safety regulations. Among other criteria are the user's need for physical mobility and autonomy. For example, active-liquid systems operate by chilling water and circulating it through a garment; the skin surface area is thereby cooled through conduction. This type of system has proven successful in certain military, law enforcement, and industrial applications. Bomb-disposal technicians wearing special suits to protect against improvised explosive devices (IEDs) use a small, ice-based chiller unit that is strapped to one leg; a liquid-circulating garment, usually a vest, is worn over the torso to maintain a safe core body temperature. By contrast, soldiers traveling in combat vehicles can face microclimate temperatures in excess of 65 °C and require a multiple-user, vehicle-powered cooling system with rapid connection capabilities. Requirements for hazmat teams, the medical community, and workers in heavy industry vary further.

Hyperthermia is generally diagnosed by the combination of unexpectedly high body temperature and a history that supports hyperthermia instead of a fever. Most commonly this means that the elevated temperature has occurred in a hot, humid environment (heat stroke) or in someone taking a drug for which hyperthermia is a known side effect (drug-induced hyperthermia). The presence of signs and symptoms related to hyperthermia syndromes, such as extrapyramidal symptoms characteristic of neuroleptic malignant syndrome, and the absence of signs and symptoms more commonly related to infection-related fevers, are also considered in making the diagnosis.

If fever-reducing drugs lower the body temperature, even if the temperature does not return entirely to normal, then hyperthermia is excluded.

The word neuroleptic originates from the Greek word lepsis ("seizure" or "fit"). Antipsychotics ( neuroleptics or tranquilizers) were investigated by the anesthesiologists De Castro and Mundeleer who coined the term neuroleptanalgesia, an anesthetic process that involves combining a major neuroleptic tranquilizer/antipsychotic with a potent opioid analgesic to produce a detached, pain-free state. This technique was widely used from the 1960s onwards, initially using a combination of phenoperidine and haloperidol, which was subsequently replaced in the early 1980s by a combination of fentanyl and droperidol. Efforts were also made to develop compounds which combined both types of activity in a single molecule. Neuroleptanalgesia results in amnesia among some, but not all, patients. The technique has become less popular with the advent of more modern procedural sedation drug combinations, though it is still rarely used today.

The progression of SPS depends on whether it is a typical or abnormal form of the condition and the presence of comorbidities. Early recognition and neurological treatment can limit its progression. SPS is generally responsive to treatment, but the condition usually progresses and stabilizes periodically. Even with treatment, quality of life generally declines as stiffness precludes many activities. Some patients require mobility aids due to the risk of falls. About 65 percent of SPS patients are unable to function independently. About ten percent of SPS patients require intensive care at some point; sudden death occurs in about the same number of patients. These deaths are usually caused by metabolic acidosis or an autonomic crisis.

Neuroleptic-induced deficit syndrome (NIDS) is a psychopathological syndrome that develops in some patients who take high doses of an antipsychotic for an extended time. It is most often caused by high-potency typical antipsychotics, but can also be caused by high doses of many atypicals, especially those closer in profile to typical ones (that have higher D dopamine receptor affinity and relatively low 5-HT serotonin receptor binding affinity), like risperidone and amisulpride.

An increased risk of tardive dyskinesia has been associated with smoking in some studies, although a negative study does exist. There seems to be a cigarette smoke-exposure-dependent risk for TD in antipsychotic-treated patients. Elderly patients are also at a heightened risk for developing TD, as are females and those with organic brain injuries or diabetes mellitus and those with the negative symptoms of schizophrenia. TD is also more common in those that experience acute neurological side effects from antipsychotic drug treatment. Racial discrepancies in TD rate also exist, with Africans and African Americans having higher rates of TD after exposure to antipsychotics. Certain genetic risk factors for TD have been identified including polymorphisms in the genes encoding the D, 5-HT and 5-HT receptors.

A Japanese man, who was being treated for schizophrenia, exhibited neuroleptics-induced deficit syndrome and obsessive–compulsive symptoms. His symptoms were remarkably improved by quitting a course of antipsychotics followed by the introduction of the antidepressant fluvoxamine. He has been misdiagnosed with schizophrenia, the real diagnosis was obsessive–compulsive disorder.