Users experience a rise in concern about their looks and worries about how others view them. Feelings of pressure to exercise to be toned and slim also increase after that time.
Academics asked 100 women how long they spent online checking Facebook, Instagram and Pinterest before giving them a detailed questionnaire on body image.
Dr Martin Graff, who led the study, said: ‘There was a thin ideal for women before social media, that has been the case for decades, but social media makes it a lot more powerful.
‘Women also use social media to compare themselves to their friends, who have filters to edit how they look.’
Dr Graff said the research showed ‘it is not just initial exposure to these sites that can cause an issue but the daily time spent on them’.
The study at the University of South Wales divided the women into four groups based on the average time they spent on social media each day, ranging from 30 minutes to more than 90 minutes.
They were asked questions such as how much they agreed that slender and toned women were attractive or if they worried whether the clothes they wore made them look good.
The results were presented at the British Psychological Society’s annual conference in Nottingham.
Previous evidence from Australia shows people can get ‘fixated’ by comparing themselves to friends on Facebook.
Academics asked 100 women how long they spent online checking Facebook, Instagram and Pinterest before giving them a detailed questionnaire on body image