Believers in alien abductions can be just as harmful to your mental health than the fact that you were actually kidnapped.

Robbie Williams and David Bowie were among the first to believe in UFOs. Many others worldwide have claimed to be victims of alien abductions.

A study found that almost half (50%) of alien abductees) meet criteria for posttraumatic stress disorder.

The proportion of kidnapped people is slightly higher.

Because they are difficult to locate, researchers could only examine 19 claims of abduction by aliens.

PTSD rate was greater for alien abductees than it was for 32 other people.

Now a study has found almost half of 'alien abductees' meet the criteria for post-traumatic stress disorder (PTSD) (stock image)

A study found that almost half (50%) of alien abductees) meet criteria for posttraumatic stress disorder (PTSD). (stock photo)

These findings show that trauma can occur even though it almost never happened.

Researchers at Zaragoza University, Spain conducted the study. They found that an emotional reaction to an impossible event could be comparable to an individual’s reaction to a true traumatic experience.

“Abductees could have an emotional reaction similar to PTSD” they said. This is because regardless of the truth or falsity in their recollections, fear is real.

Five volunteers reported being abducted by aliens. 15 others reported seeing strange lights in a sky.

Two people described interferences with television or radio, while six others remembered an ‘interference from a bedroom visitor’.

Nearly half of those who were ‘abducted’ had memory problems. This usually lasted one to three hours. However, one individual claimed that their memory was completely blank for the entire day.

More than half had memory loss from their 'abduction', typically covering one to three hours, although one person said their memory was blank for a whole day-and-a-half (stock image)

Nearly half of those who were ‘abducted’ had memory problems. This usually lasted one to three hours. However, one individual claimed that their memory was completely blank for the entire day (stock photo).

Participants were required to fill out a questionnaire to assess PTSD.

It was a rating of the severity and frequency of problems, such as nightmares or being anxious or afraid, and feeling like they were living out their abduction.

On the PTSD scale, the group of individuals who claimed to be abducted scored higher than 32 others.

A study published in Explore found that nine individuals, which is 47.3 percent of the people who were taken by aliens, fulfilled the criteria to be diagnosed with PTSD.

This is compared to the previous rate of 46% for kidnap victim.

Seven other people reported that they had experienced a near encounter with aliens. They also suffered from symptoms such as intrusive thoughts, mood swings and anxiety.

Other three people did not experience such trauma. Some claim that they were able to contact aliens and it has changed their lives.

According to the study, 10 of the men and nine women who claimed an alien abduction had less convincing claims than others. This is due to their gullibility as well as being easy led.

The study found the nine women and 10 men claiming an alien abduction were actually less 'suggestible' - a measure including gullibility and being easily led - than other people

According to the study, 10 of the men and nine women who claim an alien abduction are actually more likely to be lied about than any other person.

Study authors suggest that there could be alternative explanations to people who believe they are being taken by aliens.

There are two types: sleep paralysis and fully awake. This is when people feel like they are floating or have hallucinations.

One possible explanation is that alien abduction could be a distortion of the memory of anaesthetic-related medical procedures. This may explain why there are familiar figures with similar colours and memories of round bright lights, nudity and pain.

However, because the numbers were so small, statistical significance was not possible.

Elvis Presley said that he had seen UFOs all his life. He claimed that he was visited by aliens telepathically at the age of eight. They showed him a vision of an alien wearing white clothing singing to a crowd.

Robbie Williams is a believer in aliens. David Bowie (known for Life On Mars) said that he witnessed so many UFOs when he was a kid that he “simply got used” to them.

Most reports of abductions by aliens occur in English-speaking countries, particularly the United States.