New research has "robustly verified" a link between loot boxes and problem gambling.
Researchers at the universities of Plymouth and Wolverhampton said loot boxes "are structurally and psychologically akin to gambling".
It also found that large numbers of children are opening loot boxes.
Loot boxes are a controversial video game mechanic that encourages real-world spending on virtual goods.
Loot boxes appear in a number of video games, but it is EA's FIFA series, and in particular its money-spinning Ultimate Team mode, that has become the focal point of the debate around them. EA has always denied FIFA's loot boxes are gambling.
In Ultimate Team, players are able to spend real-world money on packs of virtual players. While EA does display pack odds - that is, the percentage chance you will get a player above a certain overall rating - you never know exactly which cards you will get.
Ultimate Team has been accused of being a pay-to-win mode because of these loot boxes, which EA has called "surprise mechanics". EA has also insisted "you can acquire all items without spending money" in Ultimate Team, but a recent Eurogamer investigation cast doubt on that claim.
The new research, commissioned by the GambleAware charity, found that of the 93 per cent of children who play video games, up to 40 per cent opened loot boxes. It also found 12 out of 13 studies on loot boxes established "unambiguous" connections to problem gambling behaviour, with young men the most likely to use loot boxes, and young age and lower education correlating with increased use.
The report said many games use a "psychological nudge" to encourage people to buy loot boxes - such as the fear of missing out on limited-time items or special deals.
This can be seen clearly in FIFA Ultimate Team, which regularly trades on FOMO by releasing powerful, coveted cards in limited quantities or for limited periods of time.
"Many gamers do ascribe discrete financial values to loot box contents - based on purchase or resale price - suggesting that many loot boxes meet existing criteria for gambling regulation," the report reads.
The report also takes aim at the "whales" element of loot box revenue. It found some can spend more than £70 a month on loot boxes, although the people doing this are not necessarily earning lots of money.
Dr James Close, senior research fellow at the University of Plymouth, said: "Our work has established that engagement with loot boxes is associated with problem gambling behaviours, with players encouraged to purchase through psychological techniques such as 'fear of missing out'. We have also demonstrated that at-risk individuals, such as problem gamblers, gamers, and young people, make disproportionate contributions to loot box revenues.
"We have made a number of policy suggestions to better manage these risks to vulnerable people, although broader consumer protections may also be required."
GambleAware's chief Zoe Osmond added: "The research has revealed that a high number of children who play video games also purchase loot boxes and we are increasingly concerned that gambling is now part of everyday life for children and young people.
"GambleAware funded this research to highlight concerns around loot boxes and problem gambling, ahead of the upcoming Gambling Act Review. It is now for politicians to review this research, as well as the evidence of other organisations, and decide what legislative and regulatory changes are needed to address these concerns."
EA has already been forced to change the way FIFA works in response to government intervention. In January 2019, EA stopped selling FIFA Points in Belgium following government pressure over loot boxes. The Netherlands Gambling Authority has also declared loot boxes illegal because they are considered a game of chance, and therefore violate the country's Gambling Act. The Dutch authorities ended up issuing EA with a fine of up to €10m over loot boxes in FIFA.
FIFA loot boxes are currently not considered a form of gambling in the UK, although the government is taking a close look at them in that context. In July, the House of Lords gambling committee urged the government to "act immediately" to regulate them. The Department for Digital, Culture, Media and Sport launched a consultation on loot boxes in September and a review of the Gambling Act 2005 in December last year. It is due to publish a white paper before the end of this year.
If the UK decides to classify loot boxes and gambling, EA may be forced to change the way Ultimate Team works at a fundamental level. The suggestion is that if EA sticks with loot boxes, it will be forced to slap FIFA with an 18+ age rating, which is obviously not something it will be willing to do. The question the publisher would then face is: how can continue to grow revenue while keeping Ultimate Team appropriate for children in the UK?
I've long called for EA to stop selling loot boxes for real-world money and switch to a battle pass system for Ultimate Team. As I wrote in our FIFA 21 review:
"Did EA not get the battle pass memo or something? Did Fortnite pass the studio by? FIFA 21 has season progress, which looks like it wants to be a battle pass, but it feels like EA pulled out of the tackle because it was frightened of getting injured. Get rid of pay-to-win loot boxes and sell a premium battle pass. Sell meaningless items. Sell celebrations. Sell kits. Sell player haircuts, for all I care. EA Sports' famous tagline is "it's in the game". Well, it's time to take pay-to-win out - and put a proper battle pass in."