American-born Dr Robert Bartholomew said the real trigger of the mass hysteria attacks early last week was a photo which depicted a "black figure", supposedly spotted at the grounds of one of the schools, that went viral on social media.
In a Google Hangout interview with Astro AWANI, Bartholomew said such images coupled with the belief of Malaysians, especially the Malays, in supernatural beings contributed to their anxiety.
READ: Hysteria at SMK Pengkalan Chepa 2
"Under stress, nerves and neurons that send messages to the brain become disrupted, messages get garbled, you get twitching, hallucinations, possession states.. all triggered by stress. It can look very real like somebody is possessed at the time, but it is in fact psychological.
"As a foreigner, as an outsider... I am not trying to change people's belief in these beings. Who knows, those supernatural creatures are real.
"Possessions happen across all religions and cultures. However, it is triggered by stress. It is a psychological phenomenon caused by anxiety," explained Bartholomew, who is also the author of Mass Hysteria in Schools published in 2014.
READ: Scaring children with stories on spirits can cause hysteria - Kelantan mufti
He said the underlying stress that causes the mass hysteria last week was the image of the "black figure" that was posted up online.
He suggested for the schools to shut down all communication channels, including social media and wi-fi, for the schools to return to normal.
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"The image itself is very vague. It can be anything. But the image is upsetting the students," he said.
Bartholomew also said engaging various bomohs to address the matter would have a rebound effect.
"Bringing in the bomoh reinforces the belief that there are supernatural being in the schools," he said.
Bartholomew said cases of hysteria should be recorded and studied, and not shunned upon.
"It is something to be understood. It is something you want to record and keep as part of your heritage.
It happens all over over the world. It should be studied. It is education," he said.
The mass hysteria attacks hit three schools in Kelantan from early last week, SMK Pengkalan Chepa 2, SMK Kubang Kerian 3 and SMK Kemumin. The incidents had affected more than 100 students and teachers.
The schools had subsequently called in several bomohs and medical practitioners to help recover the situation, but only some claimed success.
READ: Poor personal hygiene, lack of faith in Allah possible causes of mass hysteria - Expert
School authorities and the state education department, however, had said the situation was now under control with no new cases reported since.
