Twin Tower attacks
A study has linked political extremism with conspiracy theories, such as the belief 9/11 was hatched by the US government Reuters

Political extremists are most susceptible to believing conspiracy theories, such as the financial crisis being caused by a secret deal between bankers and politicians, or the Iraq war being driven by a thirst for oil, a study has suggested.

Researchers in the United States and the Netherlands found those on the far right or left have an "increased tendency to believe in conspiracy theories".

A team led by psychologist Jan-Willem van Prooijen of VU University Amsterdam concluded the theorists believe in conspiracies as a way of "making sense of societal events".

In one study, 185 participants were asked to classify themselves on a ideological scale from extremely left-wing to extremely right-wing before confirming their level of agreement or disagreement with statements.

They were then asked to rank their agreement/disagreement with that statement "the financial crisis is the result of a conspiracy between bankers and corrupt politicians" and other theories.

In another investigation, 1,010 people were asked to rate themselves on an 11-point left-right scale level of agreement or disagreement with the statement "with the correct policies, most societal problems can be solved very easily".

The same people were then presented with six conspiracy theories - including "the political arena was infiltrated by oil companies when making the decision to go to war against Iraq" - and asked to rate them on a scale of one ("highly probable") to seven ("highly improbable").

Researchers concluded people on both sides of the left-right divide, as well as those who agreed with the policies statement, were more likely to believe in the conspiracies.

The study also suggested conspiracy theorists have a propensity to look for "clear-cut" answers and have a tendency to subvert news and opinion that differed from their own.

Most discussed conspiracy theories

JFK historic images as US marks anniversary
President and Mrs. John F. Kennedy, and Texas Governor John Connally ride through Dallas moments before Kennedy was assassinated, November 22, 1963 Reuters

9/11 was an inside job - A 2005 poll found 42% of Americans thought the government was hiding the truth about the atrocity.

JFK assassination - Vice-president Lyndon Johnson, the KGB and the Mafia have all been implicated by conspiracy theorists.

Area 51 - Apparently, the remains of crashed UFO spacecrafts are stored at Area 51, an Air Force base about 150 miles from Las Vegas.

Moon landings - Filmmaker Stanley Kubrick may have helped Nasa fake the first lunar landing, given the technology used to make his 1968 film, 2001: A Space Odyssey.

Aids was man-made - Conspiracy theorists believe the the deadly virus was created by the CIA to wipe out homosexuals and African-Americans or to kill every homosexual in New York during the 1970s and 1980s.

Reptilian elite - Queen Elizabeth, George W Bush, Henry Kissinger and other world leaders are all flesh-eating reptiles, so says author David Icke and his followers.