I saw Martin (not his real name) after he was admitted to the hospital. The police had brought him in after he called them to report that he was being attacked by a group of people in his home. When the police arrived at his flat, he charged at them and had to be pinned down and cuffed.

He later explained to me that he was the victim of a conspiracy, of a nefarious network that comprised the Government, the Singapore Police Force, the Singapore Civil Defence Force, his neighbours and many others that he did not even know of. He had deliberately wanted a confrontation with the police whom he "knew" were keeping him under constant surveillance.

Prior to his admission, Martin had worked as a deliveryman. According to him, one day he began receiving messages that were coded within the sequences of the numbers on licence plates of cars on the road.

Bit by bit, they "warned" him of a conspiracy that had - quite inexplicably - sprung up and identified him as a target.

To the psychiatric team treating him in the ward, Martin was patently delusional and hence psychotic.

In psychiatry, the definition of a delusion is a false, unshakeable idea or belief that is not in keeping with the person's educational, cultural and social background. It is usually held with extraordinary conviction and is maintained despite evidence to the contrary.

This false belief is almost always not shared by others - or in our psychiatric parlance, it means that delusions have a "self-referential" component.

But Martin's psychosis was more complicated - his delusions interlocked with a set of deeply held conspiracy beliefs.

It was from him that I first heard of the Illuminati, which he informed me is a secret society of politicians, religious leaders, actors and pop stars who form a power elite that are pulling the levers of governments and shaping world events.

(According to the online Britannica, it originated from the 15th century and, through the ages, the term was used for various secret societies said to be behind various momentous historical events, including inciting the French Revolution and the assassination of President John F. Kennedy.)

The reason why Martin believed that he was being monitored by the police was that he thought the Illuminati wanted to recruit him for an unknown special mission.

Lure of conspiracy theories

Conspiracy beliefs are different from delusions: They are less self-referential, with large groups of people or even the whole world thought to be the target of this supposed plot, and these beliefs are held to be the truth by many fellow conspiracy theorists.

People are drawn to conspiracy theories especially in times of fear and anxiety. Unsurprisingly, there has been a proliferation of conspiracy theories in the United States amid racial tension and unrest kindled by police brutality and white supremacists; wildfires of biblical scale; a presidency that has been stoking myriad conspiracy theories; and the Covid-19 pandemic that has annihilated more than 370,000 Americans, and laid waste to the economy.

This has created a pervasive feeling of powerlessness.

And powerlessness leads to rage, which seeks a scapegoat.

In a situation where threats seem to lurk everywhere and when facts prove too hard to accept and too confoundingly complicated, fantasy bridges the gap between the factual and the fictional.

The slew of conspiracy theories includes the imaginary "deep state" of a shadow government working against President Donald Trump; QAnon and its theory of a satanic child-sex-trafficking ring run by high-ranking Democratic politicians and the media elite; and claims that Covid-19 was intentionally disseminated by China. Or that the pandemic was engineered by Mr George Soros and Mr Bill Gates in a plot with the World Health Organisation to "control and rule the world" with vaccines. The list goes on.

When we live in dread and are mired in a situation where we have little or no control, our minds would work in particular ways that make us susceptible to conspiracy thinking.

In studies on undergraduate students in Northwestern University in the US, participants who were asked to recall a situation where they felt out of control were more likely to see "illusory patterns" - that is, they found meaningful patterns in random stimuli and drew correlations where none was warranted.

And people who believe in conspiracy theories are more likely to do just that: They are prone to a cognitive bias called "teleological thinking", where there is a marked tendency to overattribute events to covert forces, purposes and motives.

They also have a greater need for "cognitive closure", which is a compelling desire to have an explanation when explanations are lacking.

Self-sealing logic

In some ways, conspiracy theories are alluring with their self-sealing logic unadulterated by the complexities of reality.

They give an assuring sense of control no matter how preposterous or wacky.

The possession of that insider knowledge that others lack also gives conspirators a sense of superiority and a boost to their self-esteem. And so, to University of Miami political scientist Joseph Uscinski, conspiracy theories are for "losers". By this, he means that it is a way for those who are alienated, disenfranchised and powerless to seize something from the comparatively powerful establishment.

It is easy to be condescending and to see them as obstinately ignorant, flaky, intellectually suspect and exasperatingly immune to reasoning.

And because these conspiracy theories are often melded with their political and cultural identities, debating, debunking or fact-checking someone who has imbibed them into his existence and which have given him significance and even a cause, is going to be counterproductive, and possibly even construed as a personal attack.

It is like individuals in the throes of paranoid psychosis, where confronting and arguing with them over their persecutory delusions is not only futile but often rouses animosity.

Delusions, on the other hand, can yield to treatment.

I did not challenge Martin's delusions, though I managed to persuade him to take antipsychotic medications.

His delusions resolved themselves within a short period with medication but his conspiracy beliefs persisted.

Of late, he thought that the Covid-19 pandemic is being further propagated by 5G cellular networks. He seemed fired up by these conspiracy theories, and animatedly told me during one outpatient visit that he spent hours scrolling through social media and the Internet to gather more "facts" and make contact with other conspirators.

I felt sad thinking of all that time, energy, imagination and emotion Martin had squandered chasing these various conspiracy theories.

American journalist Michael Specter had said that conspiracy theories are like untreated wounds which fester and deepen.

Claims that the Covid-19 pandemic is a hoax perpetuated to control the population have resulted in refusals to take protective measures.

Claims that 5G is responsible for coronavirus transmission have led to attacks on phone masts in various countries. And conspiracy theories that the Covid-19 vaccination is a disguised means of establishing a mass population-tracking system, through the implantation of microchips, will deter people from taking the vaccine.

At this time, when there is hope that we can turn the dark corner of this pandemic with the available coronavirus vaccines, conspiracy theories can imperil this desperately awaited recovery and lead to prolonged suffering and even more unnecessary deaths.

When there is a deep, festering wound that goes unchecked, the consequences can be deadly.

• Professor Chong Siow Ann, a psychiatrist, is vice-chairman of the medical board (research) at the Institute of Mental Health.