Two-thirds of South African teens and adults suffer from a "fear of missing out" on more interesting activities than what they're doing, a study by a pharmaceutical firm showed on Monday.

Over 62 percent of some 3,000 respondents aged between 15 and 50 years said in a nationwide survey that they live in "constant fear" of missing out on something more exciting that what they are doing.

The symptoms of the epidemic, known by its acronym FOMO, include the inability to put away one's mobile phone, excessive phone texting even while driving, tweeting on the toilet and showing up at events uninvited.

"The survey confirmed that over 62 percent of South Africans admitted that they live in constant fear of missing out (FOMO)," Pharma Dynamics spokeswoman Mariska Fouche said, adding FOMO elevates stress levels.

"People who suffer from FOMO constantly push themselves to the limit and even when we are sick, we try not to miss out on social events, we still go to work and we can't say no and this puts a lot of additional strain on our immune system that in turn heightens our risk of more serious illness," she told AFP.

The firm stumbled on the finding while studying what drove a rising demand for immune-boosting supplements.

More than a third of people surveyed said they often interrupt one call to take another and check online social sites like their Twitter stream or Facebook page while on a date, for fear that something more interesting might just be happening.

"FOMO is a blend of anxiety, inadequacy and irritation that can flare up especially while browsing social media," she said, adding the obsession has in many ways upped the demand for over-the counter vitamin supplements.

South Africans are the most enthusiastic tweeters in Africa, producing the most posts on the continent with more than five million tweets in the last three months of 2011, according to a report released in January.

Kenya and Nigeria followed in second and third place.