Dancing mania (also known as dancing plague, choreomania, St John's Dance and, historically, St. Vitus's Dance) was a social phenomenon that occurred primarily in mainland Europe between the 14th and 17th centuries. It involved groups of people dancing erratically, sometimes thousands at a time. The mania affected men, women, and children who danced until they collapsed from exhaustion. One of the first major outbreaks was in Aachen, in the Holy Roman Empire, in 1374, and it quickly spread throughout Europe; one particularly notable outbreak occurred in Strasbourg in 1518, also in the Holy Roman Empire.

Affecting thousands of people across several centuries, dancing mania was not an isolated event, and was well documented in contemporary reports. It was nevertheless poorly understood, and remedies were based on guesswork. Generally, musicians accompanied dancers, to help ward off the mania, but this tactic sometimes backfired by encouraging more to join in. There is no consensus among modern-day scholars as to the cause of dancing mania.

The several theories proposed range from religious cults being behind the processions to people dancing to relieve themselves of stress and put the poverty of the period out of their minds. It is, however, thought to have been a mass psychogenic illness in which the occurrence of similar physical symptoms, with no known physical cause, affect a large or small group of people as a form of social influence.

For women taking psychiatric medication, the decision as to whether continue during pregnancy and whether to take them while breast feeding is difficult in any case; there is no data to guide this decision with respect to preventing postpartum psychosis. There is no data to guide a decision as to whether women at high risk for postpartum psychosis should take antipsychotic medicine to prevent it. For women at risk of postpartum psychosis, informing medical care-givers, and monitoring by a psychiatrist during pregnancy, in the perinatal period, and for a few weeks following delivery, is recommended.

For women with known bipolar disorder, taking medication during pregnancy roughly halves the risk of a severe postpartum episode, as does starting to take medication immediately after the birth.

In Italy, a similar phenomenon was tarantism, in which the victims were said to have been poisoned by a tarantula or scorpion. Its earliest known outbreak was in the 13th century, and the only antidote known was to dance to particular music to separate the venom from the blood. It occurred only in the summer months. As with dancing mania, people would suddenly begin to dance, sometimes affected by a perceived bite or sting and were joined by others, who believed the venom from their own old bites was reactivated by the heat or the music. Dancers would perform a tarantella, accompanied by music which would eventually "cure" the victim, at least temporarily.

Some participated in further activities, such as tying themselves up with vines and whipping each other, pretending to sword fight, drinking large amounts of wine, and jumping into the sea. Some died if there was no music to accompany their dancing. Sufferers typically had symptoms resembling those of dancing mania, such as headaches, trembling, twitching and visions.

As with dancing mania, participants apparently did not like the color black, and women were reported to be most affected. Unlike dancing mania, tarantism was confined to Italy and southern Europe. It was common until the 17th century, but ended suddenly, with only very small outbreaks in Italy until as late as 1959.

A study of the phenomenon in 1959 by religious history professor Ernesto de Martino revealed that most cases of tarantism were probably unrelated to spider bites. Many participants admitted that they had not been bitten, but believed they were infected by someone who had been, or that they had simply touched a spider. The result was mass panic, with a "cure" that allowed people to behave in ways that were, normally, prohibited at the time. Despite their differences, tarantism and dancing mania are often considered synonymous.

Several studies have shown that the risk of suicide is higher in patients who suffer from Bipolar II than those who suffer from Bipolar I, and especially higher than patients who suffer from major depressive disorder.

In results of a summary of several lifetime study experiments, it was found that 24% of Bipolar II patients experienced suicidal ideation or suicide attempts compared to 17% in Bipolar I patients and 12% in major depressive patients. Bipolar disorders, in general, are the third leading cause of death in 15- to 24-year-olds. Bipolar II patients were also found to employ more lethal means and have more complete suicides overall.

Bipolar II patients have several risk factors that increase their risk of suicide. The illness is very recurrent and results in severe disabilities, interpersonal relationship problems, barriers to academic, financial, and vocational goals, and a loss of social standing in their community, all of which increase the likelihood of suicide. Mixed symptoms and rapid-cycling, both very common in Bipolar II, are also associated with an increased risk of suicide. The tendency for Bipolar II to be misdiagnosed and treated ineffectively, or not at all in some cases, leads to an increased risk.

As a result of the high suicide risk for this group, reducing the risk and preventing attempts remains a main part of the treatment; a combination of self-monitoring, close supervision by a therapist, and faithful adherence to their medication regimen will help to reduce the risk and prevent the likelihood of a completed suicide.

Women with a history of bipolar disorder, schizophrenia, prior episode of postpartum psychosis, or a family history of postpartum psychosis are at high risk; about 25-50% of women in this group will have postpartum psychosis. around 37% of women with bipolar disorder have a severe postpartum episode. Women with a prior episode of postpartum psychosis have about a 30% risk of having another episode in the next pregnancy. For a woman with no history of mental illness who has a close relative (a mother or sister) who had postpartum psychosis, the risk is about 3%. There may be a genetic component; while mutations in chromosome 16 and in specific genes involved in serotoninergic, hormonal, and inflammatory pathways have been identified, none had been confirmed as of 2014.

Family history of affective psychosis, prenatal depression, and autoimmune thyroid dysfunction also increase the risk of postpartum psychosis.

About half of women who experience postpartum psychosis had no risk factors. Many other potential factors like pregnancy and delivery complications, caesarean section, sex of the baby, length of pregnancy, changes in psychiatric medication, and psychosocial factors have been researched and no clear association has been found; the only clear risk factor identified as of 2014 was that postpartum psychosis happens more often to women giving birth for the first time, than to women having second or subsequent deliveries, but the reason for that was not known. There may be a role for hormonal changes that occur following delivery, in combination with other factors; there may be a role changes in the immune system as well.

The exact incidence and prevalence of brief psychotic disorder is not known, but it is generally considered uncommon. Internationally, it occurs twice as often in women than men, and even more often in women in the United States. It typically occurs in the late 30s and early 40s. The exact cause of brief psychotic disorder is not known. One theory suggests a genetic link, because the disorder is more common in people who have family members with mood disorders, such as depression or bipolar disorder. Another theory suggests that the disorder is caused by poor coping skills, as a defense against or escape from a particularly frightening or stressful situation. These factors may create a vulnerability to develop brief psychotic disorder. In most cases, the disorder is triggered by a major stress or traumatic event. Childbirth may trigger the disorder in some women. Approximately 1 in 10,000 women experience brief psychotic disorder shortly after childbirth. There are general medical causes of brief psychosis that should also be considered when being evaluated. Post-natal depression, HIV and AIDS, malaria, syphilis, Alzheimer's disease, Parkinson's disease, hypoglycaemia (an abnormally low level of glucose in the blood), lupus, multiple sclerosis, brain tumor and PANS.

Schizoaffective disorder is estimated to occur in 0.5 to 0.8 percent of people at some point in their life. It is more common in women than men; however, this is because of the high concentration of women in the depressive subcategory, whereas the bipolar subtype has a more or less even gender distribution.

Comorbid conditions are extremely common in individuals with BP-II. In fact, individuals are twice as likely to present a comorbid disorder than not. These include anxiety, eating, personality (cluster B), and substance use disorders. For bipolar II disorder, the most conservative estimate of lifetime prevalence of alcohol or other drug abuse disorders is 20%. In patients with comorbid substance abuse disorder and BP-II, episodes have a longer duration and treatment compliance decreases. Preliminary studies suggest that comorbid substance abuse is also linked to increased risk of suicidality.

In researching over 1000 individuals of vast range of backgrounds, Stompe and colleagues (2006) found that grandiosity remains as the second most common delusion after persecutory delusions. A variation in the occurrence of grandiosity delusions in schizophrenic patients across cultures has also been observed. In research done by Appelbaum "et al." it has been found that GDs appeared more commonly in patients with bipolar disorder (59%) than in patients with schizophrenia (49%), followed by presence in substance misuse disorder patients (30%) and depressed patients (21%).

A relationship has been claimed between the age of onset of bipolar disorder and the occurrence of GDs. According to Carlson "et al." (2000), grandiose delusions appeared in 74% of the patients who were 21 or younger at the time of the onset, while they occurred only in 40% of individuals 30 years or older at the time of the onset.

Ideas of reference and delusions of reference describe the phenomenon of an individual's experiencing innocuous events or mere coincidences and believing they have strong personal significance. It is "the notion that everything one perceives in the world relates to one's own destiny".

In psychiatry, delusions of reference form part of the diagnostic criteria for psychotic illnesses such as schizophrenia, delusional disorder, bipolar disorder (during the elevated stages of mania), as well as schizotypal personality disorder. To a lesser extent, it can be a hallmark of paranoid personality disorder. Such symptoms can also be caused by intoxication, especially with hallucinogens or stimulants like methamphetamine.

A clear causal connection between drug use and psychotic spectrum disorders, including schizoaffective disorder, has been difficult to prove. In the specific case of marijuana or cannabis, however, evidence supports a link between earlier onset of psychotic illness and cannabis use. The more often cannabis is used, particularly in early adolescence, the more likely a person is to develop a psychotic illness, with frequent use being correlated with double the risk of psychosis and schizoaffective disorder. A 2009 Yale review stated that in individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. While cannabis use is accepted as a contributory cause of schizoaffective disorder by many, it remains controversial, since not all young people who use cannabis later develop psychosis, but those who do use cannabis have an increased odds ratio of about 3.

There is evidence that the two major component cannabinoids in cannabis have different effects: tetrahydrocannabinol (THC), which causes a "high," may increase propensity to psychosis; while cannabidiol (CBD), which doesn't cause a "high" and may have neuroprotective effects—that is, reduce psychosis and have mood stabilizing effects.

About half of those with schizoaffective disorder use drugs or alcohol excessively. There is evidence that alcohol abuse via a kindling mechanism can occasionally cause the development of a chronic substance induced psychotic disorder, i.e. schizoaffective disorder. There is little evidence to suggest that psychotic individuals choose specific drugs to self-medicate; there is some support for the hypothesis that they use drugs to cope with unpleasant states such as depression, anxiety, boredom and loneliness.

Amphetamine, cocaine, and to a lesser extent alcohol, can result in psychosis that presents clinically like psychosis in schizoaffective disorder. It is well understood that methamphetamine and cocaine use can result in methamphetamine or cocaine-induced psychosis that may persist even when users remain abstinent. Alcohol-induced psychosis can also persist during abstinence, though it appears to do so at a lower rate, than when it is being abused.

Although it is not generally believed to be a cause of the illness, people with schizoaffective disorder use nicotine at much greater rates than the general population.

Bipolar disorder can cause suicidal ideation that leads to suicidal attempts. Individuals whose bipolar disorder begins with a depressive or mixed affective episode seem to have a poorer prognosis and an increased risk of suicide. One out of two people with bipolar disorder attempt suicide at least once during their lifetime and many attempts are successfully completed. The annual average suicide rate is 0.4 percent, which is 10–20 times that of the general population. The standardized mortality ratio from suicide in bipolar disorder is between 18 and 25. The lifetime risk of suicide has been estimated to be as high as 20 percent in those with bipolar disorder.

The hypothesis that those prone to extroversion or neuroticism, or those with low IQ scores, are more likely to be affected in an outbreak of hysterical epidemic has not been consistently supported by research. Bartholomew and Wesseley state that it “seems clear that there is no particular predisposition to mass sociogenic illness and it is a behavioural reaction that anyone can show in the right circumstances.”

Females are affected with mass psychogenic illness at greater rates than males. Adolescents and children are frequently affected in cases of MPI.

Lovesickness refers to an informal affliction that describes negative feelings associated with rejection, unrequited love or the absence of a loved one. It can manifest as physical as well as mental symptoms. It is not to be confused with the condition of being lovestruck, which refers to the physical and mental symptoms associated with falling in love. The term lovesickness is rarely used in medical or psychological fields.

Many people believe lovesickness was created as an explanation for longings, but it can be associated with depression and various mental health problems.

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.

According to a substantial amount of epidemiology studies conducted, women are twice as likely to develop certain mood disorders, such as major depression. Although there is an equal number of men and women diagnosed with bipolar II disorder, women have a slightly higher frequency of the disorder.

In 2011, mood disorders were the most common reason for hospitalization among children aged 1–17 years in the United States, with approximately 112,000 stays. Mood disorders were top principal diagnosis for Medicaid super-utilizers in the United States in 2012. Further, a study of 18 States found that mood disorders accounted for the highest number of hospital readmissions among Medicaid patients and the uninsured, with 41,600 Medicaid patients and 12,200 uninsured patients being readmitted within 30 days of their index stay—a readmission rate of 19.8 per 100 admissions and 12.7 per 100 admissions, respectively. In 2012, mood and other behavioral health disorders were the most common diagnoses for Medicaid-covered and uninsured hospital stays in the United States (6.1% of Medicaid stays and 5.2% of uninsured stays).

A study conducted in 1988 to 1994 amongst young American adults involved a selection of demographic and health characteristics. A population-based sample of 8,602 men and women ages 17–39 years participated. Lifetime prevalence were estimated based on six mood measures:

1. major depressive episode (MDE) 8.6%,

2. major depressive disorder with severity (MDE-s) 7.7%,

3. dysthymia 6.2%,

4. MDE-s with dysthymia 3.4%,

5. any bipolar disorder 1.6%, and

6. any mood disorder 11.5%.

Research suggests that the severity of the delusions of grandeur is directly related to a higher self-esteem in individuals and inversely related to any individual’s severity of depression and negative self-evaluations. Lucas "et al." found that there is no significant gender difference in the establishment of grandiose delusion. However, there is a claim that ‘the particular component of Grandiose delusion’ may be variable across both genders. Also, it had been noted that the presence of GDs in people with at least grammar or high school education was greater than lesser educated persons. Similarly, the presence of grandiose delusions in individuals who are the eldest is greater than in individuals who are the youngest of their siblings.

When the Malays were asked why they thought that women were more likely to suffer from latah, they responded with the cultural explanation that women have less 'semangat' or soul substance. They also said women are simply easier to tease than men, and coupling these two together: latah becomes more readily observable and developed throughout recurrent provocation in women than in men. This also accounts for the higher prevalence of latah in lower status persons, as they are more vulnerable to abuse than others. The Malay also believe women are more susceptible because they lose more blood than men, through menstruation. Some Malay believe that excess tickling of a child will predispose them to latah later in life.

Excited delirium occurs most commonly in males with a history of serious mental illness or acute or chronic drug abuse, particularly stimulant drugs such as cocaine and MDPV. Alcohol withdrawal or head trauma may also contribute to the condition.

A majority of fatal case involved men.

People with excited delirium commonly have acute drug intoxication, generally involving PCP, methylenedioxypyrovalerone (MDPV), cocaine, or methamphetamine. Other drugs that may contribute to death are antipsychotics.

Various triggers have been associated with switching from euthymic or depressed states into mania. One common trigger of mania is antidepressant therapy. Studies show that the risk of switching while on an antidepressant is between 6-69% percent. Dopaminergic drugs such as reuptake inhibitors and dopamine agonists may also increase risk of switch. Other medication possibly include glutaminergic agents and drugs that alter the HPA axis. Lifestyle triggers include irregular sleep wake schedules and sleep deprivation, as well as extremely emotional or stressful stimuli.

Various genes that have been implicated in genetic studies of bipolar have been manipulated in preclinical animal models to produce syndromes reflecting different aspects of mania. CLOCK and DBP polymorphisms have been linked to bipolar in population studies, and behavioral changes induced by knockout are reversed by lithium treatment. Metabotropic glutamate receptor 6 has been genetically linked to bipolar, and found to be under-expressed in the cortex. Pituitary adenylate cyclase-activating peptide has been associated with bipolar in gene linkage studies, and knockout in mice produces mania like-behavior. Targets of various treatments such as GSK-3, and ERK1 have also demonstrated mania like behavior in preclinical models.

Mania may be associated with strokes, especially cerebral lesions in the right hemisphere.

Deep brain stimulation of the subthalamic nucleus in Parkinson's Disease has been associated with mania, especially with electrodes placed in the ventromedial STN. A proposed mechanism involves increased excitatory input from the STN to dopaminergic nuclei.

The causes of bipolar disorder likely vary between individuals and the exact mechanism underlying the disorder remains unclear. Genetic influences are believed to account for 60–80 percent of the risk of developing the disorder indicating a strong hereditary component. The overall heritability of the bipolar spectrum has been estimated at 0.71. Twin studies have been limited by relatively small sample sizes but have indicated a substantial genetic contribution, as well as environmental influence. For bipolar disorder type I, the rate at which identical twins (same genes) will both have bipolar disorder type I (concordance) is estimated at around 40 percent, compared to about 5 percent in fraternal twins. A combination of bipolar I, II, and cyclothymia similarly produced rates of 42 percent and 11 percent (identical and fraternal twins, respectively), with a relatively lower ratio for bipolar II that likely reflects heterogeneity. There is overlap with major (unipolar) depression and if this is also counted in the co-twin the concordance with bipolar disorder rises to 67 percent in identical twins and 19 percent in fraternal twins. The relatively low concordance between fraternal twins brought up together suggests that shared family environmental effects are limited, although the ability to detect them has been limited by small sample sizes.

The pathophysiology of excited delirium has been unclear, but likely involves multiple factors. These may include positional asphyxia, hyperthermia, drug toxicity, and/or catecholamine-induced fatal cardiac arrhythmias.

Dipsomania is a historical term describing a medical condition involving an uncontrollable craving for alcohol. In the 19th century, the term dipsomania was used to refer to a variety of alcohol-related problems, most of which are known today as alcoholism. Dipsomania is occasionally still used to describe a particular condition of periodic, compulsive bouts of alcohol intake. The idea of dipsomania is important for its historical role in promoting a disease theory of chronic drunkenness. The word comes from Greek "dipso" ("δίψα"= thirst) and "mania".

It is still mentioned in the WHO ICD-10 classification as an alternative description for Alcohol Dependence Syndrome, episodic use F10.26

The condition is rare, with only 80 established cases reported in medical literature and incomplete evidence of a further 200.

Mass psychogenic illness (MPI), also called mass sociogenic illness or just sociogenic illness, is "the rapid spread of illness signs and symptoms affecting members of a cohesive group, originating from a nervous system disturbance involving excitation, loss, or alteration of function, whereby physical complaints that are exhibited unconsciously have no corresponding organic" cause. MPI is distinct from other collective delusions, also included under the blanket terms of mass hysteria, in that MPI causes symptoms of disease, though there is no organic cause.

There is a clear preponderance of female victims. The DSM-IV-TR does not have specific diagnosis for this condition but the text describing conversion disorder states that "In 'epidemic hysteria', shared symptoms develop in a circumscribed group of people following 'exposure' to a common precipitant."