According to some experts, the symptoms can be divided into two categories: anxiety symptoms which are usually short-lived and motor symptoms which usually persist over a longer period of time. The most commonly reported symptoms include headache, dizziness, nausea, abdominal cramping, and cough.

There are several observed patterns in mass hysteria cases. Females are disproportionately affected and so are adolescents and children. The episodes occur after an environmental trigger such as an odour, rumour, etc., and patients who have recently suffered a physical or psychological stress are more vulnerable than others.

In the Blackburn case, a previous polio epidemic had rendered the population emotionally vulnerable and a three-hour long parade had been the specific trigger. Also, the incidence rate was higher amongst young girls who were high on extroversion and neuroticism on the Eysenck Personality Inventory.

An outbreak of ‘mass hysteria by proxy’ has also been documented in which anxiety transmitted among parents led to reports of symptoms in the children. In a school in Georgia, parents complained of a toxic gas that they believed was the cause of illness in their children. Several trivial gas leaks had occurred, but all had been immediately corrected. The children showed symptoms such as included headache, sore throat, cough etc which peaked 2-4 weeks after a known gas leak had happened.

However, a review of the records showed that there was no increased illness, medical referrals, absenteeism etc caused by childhood illnesses during this time. A CDC investigation failed to find any toxic gas or other environmental cause for the symptoms.

While cases of female mass hysteria are greater in number, one of the largest cases was reported in the San Diego military barracks in which about 1000 recruits reported symptoms and CPR had to be performed on many. Those who watched CPR being performed had a higher rate of developing the  symptoms. Nearly all recovered after 24 hours and no environmental toxin etc could be pointed out as probable cause.

Mass hysteria has also been described as an expensive phenomenon by many. The economic resources and manpower needed to treat so many cases is huge which might be a burden too high to bear for developing countries. Also, the investigations conducted to rule out environmental toxins or epidemics leading to the symptoms require a lot of capital. Moreover, the symptoms of mass hysteria are very similar to other illnesses; hence the cost of litigation and monetary compensation is also factored in while making diagnosis which further complicates matters.

Cases of mass hysteria have been reported in India as well such as the 2006 Mumbai sweet seawater incident, the 1995 Hindu Milk Miracle and the 2001 Monkey Man of Delhi.

Mass hysteria can occur in normal healthy individuals as well without any underlying psychopathology. Firstly, a physical examination and laboratory testing is very important to establish that the basis of symptoms is not physical in nature and it is truly a case of hysteria. It is also important to separate those who are already showing the symptoms from the others who are not otherwise it simply spreads as in the case of the San Diego military barracks.

Proper communication of the problem to the patient is essential as well as the reassurance that a particular rumour does not serve as the basis of confirmation of a particular event. Public health authorities need to be made aware of the outbreak but confidentiality should be given its due importance. The significance and implications of mass hysteria in a modern, globalised and communicative world are immense; and this realization is of great value not only to health professionals but also to the economies as well.

(This column has research contributed by Arushi Kothari.)