It's easy to recognize the symptoms: The sigh of envy at a friend's tropical vacation photos on Facebook. The left-out feeling upon seeing Instagram evidence of a peer's latest party. The wild desire to buy a ticket to a concert that everyone seems to be going to.

The cause of those emotions, known as FOMO, or fear of missing out, has become part and parcel of today's social media-fueled universe. In 2013, the Oxford English Dictionary even added FOMO to its lexicon, reflecting growing millennial anxiety about possibly missing exciting or interesting events happening around them, particularly those shared on social media.

Over the past five years, however, the FOMO phenomenon has flourished unabated: In a recent study, for example, nearly 40 percent of Americans ages 18 to 34 said they overspend just to combat FOMO. And Eventbrite's study, "Millennials: Fueling the Experience Economy," found that nearly seven in 10 millennials experience FOMO. Not surprisingly, marketers have been hot on the heels of this trend, seeking ways to tap into their customers' strong feelings stirred up by FOMO.

Playing Into Consumers' Anxieties