Latah, from Southeast Asia, is a condition in which abnormal behaviors result from a person experiencing a sudden shock. When surprised, the affected person typically engages in such behaviors as screaming, cursing, dancing type movements, and uncontrollable laughter, and will typically mimic the words or actions of those around them. Physical symptoms include an increased heart rate and profuse sweating, but no clear physiological source has been identified.

Latah is considered a culture-specific startle disorder that was historically regarded as personal difference rather than an illness.

Similar conditions have been recorded within other cultures and locations. For example, there are the so-called Jumping Frenchmen of Maine, the women of the Ainu people of Japan ("imu"), the Siberian ("miryachit"), and the Filipino and Thai peoples; however, the connection among these syndromes is controversial.

Latah can affect people differently; someone can have a very strong reaction or a slight reaction during a latah episode. Every instance of latah has been acquired over time. Those who are affected, which by an overwhelming number are middle-to-older-aged women, are not born latah. It typically occurs around the time of menopause. There is a lack of latah in the higher social strata of Malay and Java, which suggests they are more likely to suppress their responses than those who belong to lower social classes.

A latah episode occurs after a startle of some sort (poking, shouting, something falling). During an episode, a latah person will begin to shout obscenities, imitate words or gestures of those around them or even those on TV, and will often obey any commands given to them – no matter how outrageous or against cultural norms they are. Persons with latah make movements reminiscent of behaviors normally peculiar to certain childhood developmental stages. The person is unlikely to remember anything occurring during the episode.

Running amok, sometimes referred to as simply amok or gone amok, also spelled amuk, from the Malay language, is "an episode of sudden mass assault against people or objects usually by a single individual following a period of brooding that has traditionally been regarded as occurring especially in Malay culture but is now increasingly viewed as psychopathological behavior". The syndrome of "Amok" is found in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV TR). The phrase is often used in a less serious manner when describing something that is wildly out of control or causing a frenzy (e.g., a dog tearing up the living room furniture might be termed as "running amok".)

In 1849, amok was officially classified as a psychiatric condition based on numerous reports and case studies that showed the majority of individuals who committed amok were, in some sense, mentally ill. The modern DSM-IV method of classification of mental disorders contains two official types of amok disorder; beramok and amok. Beramok is considered to be the more common of the two and is associated with the depression and sadness resulting from a loss and the subsequent brooding process. Loss includes, but is not limited to, the death of a spouse or loved one, divorce, loss of a job, money, power, etc. Beramok is associated with mental issues of severe depression or other mood disorders. Amok, the rarer form, is believed to stem from rage, insult, or a vendetta against a person, society, or object for a wide variety of reasons. Amok has been more closely associated with psychosis, personality disorders, bipolar disorder, and delusions.

Jumping Frenchmen of Maine syndrome must be distinguished from other conditions involving the startle reflex or tics.

Tourette syndrome is characterized by multiple physical (motor) tics and at least one vocal (phonic) tic. There are many overlaps when compared clinically, but the abnormal "jumping" response is always provoked, unlike the involuntary tics in Tourette syndrome.

Latah from Southeast Asia is a disorder where one's startle response is similar to a state of trance with repetitive speech or movements. Miryachit is a disorder found in Siberia that also displays an action similar to "jumping". Neurasthenia is a disorder with a startle response during periods of great fatigue.

Hyperekplexia is an extremely rare autosomal dominant neurological disease. The symptoms start in infancy with hypertonia, an abnormal muscle tension that decreases flexibility, and an exaggerated startle in all ages of life.

George Miller Beard recorded individuals who would obey any command given suddenly, even if it meant striking a loved one; the Jumping Frenchmen seemed to react abnormally to sudden stimuli. The more common and less intense symptoms consisted of jumping, yelling, and hitting. These individuals exhibited outrageous bursts, and many described themselves as ticklish and shy. Other cases involved echolalia (repeating vocalizations made by another person) and echopraxia (repeating movements made by another person). Beard noted that the men were "suggestible" and that they "could not help repeating the word or sounds that came from the person that ordered them any more than they could help striking, dropping, throwing, jumping, or starting".

Brief psychotic disorder is a period of psychosis whose duration is generally shorter, is not always non-recurring, but can be, and is not caused by another condition.

The disorder is characterized by a sudden onset of psychotic symptoms, which may include delusions, hallucinations, disorganized speech or behavior, or catatonic behavior. The symptoms must not be caused by schizophrenia, schizoaffective disorder, delusional disorder or mania in bipolar disorder. They must also not be caused by a drug (such as amphetamines) or medical condition (such as a brain tumor). The term bouffée délirante describes an acute nonaffective and nonschizophrenic psychotic disorder, which is largely similar to DSM-III-R and DSM-IV brief psychotic and schizophreniform disorders.

Symptoms generally last at least a day, but not more than a month, and there is an eventual return to full baseline functioning. It may occur in response to a significant stressor in one's life, or in other situations where a stressor is not apparent, including in the weeks following birth. In diagnosis, a careful distinction is considered for culturally appropriate behaviors, such as religious beliefs and activities. It is believed to be connected to or synonymous with a variety of culture-specific phenomena such as latah, koro, and amok.

There are three forms of brief psychotic disorder:

1. Brief psychotic disorder with a stressor, such as a trauma or death in the family.

2. Brief psychotic disorder without a stressor, there is no obvious stressor.

3. Brief psychotic disorder with postpartum onset. Usually occurs about four weeks after giving birth.

Echopraxia (also known as echokinesis) is the involuntary repetition or imitation of another person's actions. Similar to echolalia, the involuntary repetition of sounds and language, it is one of the echophenomena ("automatic imitative actions without explicit awareness"). It has long been recognized as a core feature of Tourette syndrome, and is considered a complex tic, but it also occurs in autism spectrum disorders, schizophrenia and catatonia, aphasia, and disorders involving the startle reflex such as Latah. Echopraxia has also been observed in individuals with frontal lobe damage, epilepsy, dementia and autoimmune disorders; the causes of and the link between echopraxia and these disorders is undetermined.

The etymology of the term is from Ancient Greek: " (ēkhō) from (ēkhē "sound") and " (praksis, "action, activity, practice)".

Echopraxia is a typical symptom of Tourette syndrome but causes are not well elucidated.

One theoretical cause subject to ongoing debate surrounds the role of the mirror neuron system (MNS), a group of neurons in the inferior frontal gyrus (F5 region) of the brain that may influence imitative behaviors, but no widely accepted neural or computational models have been put forward to describe how mirror neuron activity supports cognitive functions such as imitation.