Nomophobia is a word for the fear of, or anxiety caused by, not having a working mobile phone. It has been considered a symptom or syndrome of problematic digital media use in mental health, the definitions of which are not standardized.

The term, an abbreviation for "no-mobile-phone phobia," was coined during a 2008 study by the UK Post Office who commissioned YouGov, a UK-based research organization, to evaluate anxieties suffered by mobile phone users. The study found that nearly 53% of mobile phone users in Britain tend to be anxious when they "lose their mobile phone, run out of battery or credit, or have no network coverage".

The study, sampling 2,163 people, found that about 58% of men and 47% of women suffer from the phobia, and an additional 9% feel stressed when their mobile phones are off. 55% of those surveyed cited keeping in touch with friends or family as the main reason that they got anxious when they could not use their mobile phones. The study compared stress levels induced by the average case of nomophobia to be on-par with those of "wedding day jitters" and trips to the dentist.

Additionally, nomophobia's third factor—the fear of not being able to access information—has the greatest impact on the likelihood of engaging in illegal use while driving. Nomophobia occurs in situations when an individual experiences anxiety due to the fear of not having access to a mobile phone.

More Info: en.m.wikipedia.org