Being near the higher end of that age range, I distinctly remember that I stopped being a happy kid once I started using the Internet (at around age 12) even before addictive algorithmic feeds. This statistic does not surprise me in the slightest.
imo computers and the internet are such potent dopamine feeds that our brains get used to the constant stimulation, making real life boring and causing us to be anxious when we’re not getting our fix. And this is heightened when we use the computer as an alternate world to escape to, and feel more comfortable in, when we don’t feel safe or welcomed in reality.