Image copyright Megon Dew Image caption Cardiff model Megon usually takes a couple of selfies a week

Compulsive posting of selfies on social media can cause narcissistic behaviour, new research has said.

A Swansea University study claimed people who repeatedly post photos and videos of themselves online showed a 25% increase in narcissistic traits.

Its department of psychology monitored social media use of 74 people over a four-month period.

TV personality Lauren Harries, 40, from Cardiff, said selfies were "necessary" to show her new looks to her followers.

But she agreed they could make people more narcissistic.

Hallmarks of narcissism include grandiose exhibitionism, beliefs relating to entitlement and a need for admiration.

Ms Harries said: "I have had so many photos taken over the years, I am a perfectionist."

She said because she represents the transgender community, she has a responsibility to her fans.

Image copyright Lauren Harries Image caption Lauren Harries says she occasionally takes a selfie for Instagram

But Cardiff model Megan Dew disagrees and said although selfies were displays of vanity, they help improved confidence in people's body image.

The 20-year-old said the hundreds of selfies she has taken have not made her narcissistic.

Ms Dew, who has got modelling jobs from her Instagram page, said: "When you take a lot of pictures of yourself, you notice things in your face more. But I wouldn't say this makes you self-obsessed.

"I can still sit there and pick apart things I absolutely hate about a photo of myself."

She said when she was at school, girls would say "negative things" about her image or weight, so selfies help her care less about what other people think.

Image copyright Charlee Thomas Image caption Swansea blogger Charlee Thomas has been taking selfies since she was 12

Selfies also help with loneliness and making friends online, according to 24-year-old Swansea blogger Charlee Thomas.

The marketing account assistant said people "tend to interact more" with her selfies online, commenting on her outfit or lipstick.

"You get a feel-good factor from it and confidence boost. It can be addictive but I wouldn't say that selfies have changed me," she said.

Prof Phil Reed, who headed the joint project with Milan University, said: "We hope the results can be used for preventative actions."

Participants, aged 18 to 34, were asked to answer 40 questions about their perception of themselves.

"Until this study, it was not known if narcissists use this form of social media more, or whether using such platforms is associated with the subsequent growth in narcissism," Prof Reed said.

"The results of this study suggest that both occur, but show that posting selfies can indeed increase narcissism."