Some researchers embrace a belief that users of video games often experience elevated dopamine levels while competing against machines and peers, according to the Chicago Tribune.

While researchers have yet to conclude that video gaming is addictive, dopamine, at a bare minimum, is likely to entice gamers to increase the amount of time that they spend in digital competition. The concerns come at a time when many brands are making a big effort to push digital ads to video gamers, which is often called “in-game advertising.”

In February, Activision Blizzard, which is well known for its “Call of Duty” game, completed its $6 billion acquisition of King, which owns the blockbuster game series called “Candy Crush.” The deal made Activision the world’s largest video game network. Perhaps more importantly, it is providing Activision with an opportunity to pitch digital advertisements to some 463 million gamers, reports Reuters.

Some analysts maintain that the strategy could generate $500 million annually in revenue. The gaming market is already huge. Mobile video gaming has a bigger audience than prime time viewers on ABC, CBS, and NBC, according to Chartboost, which provides a gaming network with more than 800 million monthly users. The company maintains that 47% of mobile gamers shop online for more than three hours a week compared to only 28% of non-gamers.

The company believes 77% of mobile device users will play video games at least once a month by 2020. Many analysts say the rise of virtual reality and the growth of eSports, which charge spectators to watch gaming contests, are likely to provide considerable support to the industry. Indeed, late last year, an eSports competition in Chicago attracted 12 million more viewers than the 2016 NBA finals, according to the Daily Mail.

Last year, eSports generated $696 million, of which more than $500 million was from advertising and sponsorship spending. The popularity of mobile phones and other portable devices is also fueling the growth of gaming as individuals seek to stay connected with friends and family members online.

For brands, the unique nature of in-game advertising offers various advantages. Individuals who click on incentive ads, for example, receive game credits. The strategy is commonly believed to boost engagement. Other advertisements capture viewers’ attention by appearing at suspenseful moments, such as when gamers reach new skill levels. Gamers also enjoy taking short breaks, during which some individuals may actually welcome sponsored content.

Those factors help explain why in-game advertisements tend to have higher click-through rates than digital ads that appear elsewhere. With that in mind, many big brands already have well established in-game marketing programs.

RapidFire, which operates an in-game advertising network, touts Disney, Paramount, Esso, T-Mobile, and RedBull as clients. Regardless of whether or not video gaming is ever deemed to be addictive, it is clearly appealing to individuals who are prone to compulsive behavior. Within the gaming community, many individuals are obsessed with the recreational technology. Even for less compulsive individuals, the growing appeal of online entertainment is likely to support the rapid growth of gaming and therefore in-game advertising.