The term was first coined in a spoof news article in 2014 which suggested the American Psychiatric Association was considering classifying selfitis as a disorder.
Researchers have now looked into the phenomenon and say their study "validates its existence".
They examined 400 people from India - the country with the most Facebook users - and produced a "Selfitis Behaviour Scale" listing factors that provoke the condition.
This included self-confidence, attention seeking and social competition.
The paper, published in the International Journal of Mental Health and Addiction, said: "As with internet addiction, the concepts of selfitis and selfie addiction started as a hoax, but recent research including the present paper has begun to empirically validate its existence."
Researchers say the study, co-written by Dr Mark Griffiths of Nottingham Trent University, will help understanding of "human-computer interaction across mobile electronic devices".
It also argues selfie-taking may evolve over time as technology advances.
:: Photographer Rankin: Selfie craze reflects 'huge wave of narcissism'
Selfitis is not the first technology-related disorder to be studied.
"Nomophobia" - the phobia of not having a mobile phone to hand - was examined by researchers in Hong Kong who asked people to describe how they felt about their phones.
Words such as "hurt'" and "alone" predicted higher levels of nomophobia, according to the study.