To try and explain the situation the best I can imagine one of those sci-fi/fantasy situations where whenever someone is asleep they can experience new things. Whether they somehow end up in some dream world whenever they fall asleep or are plugged into some kind of virtual reality device, that person can spend days in this other world while only hours pass for them in the "real world".
My understanding of human psychology and its development isn't great, but I can notice a weird issue immediately. If the "dream reality" experiences flow at the same rate as real life (1 hour passes in the dream for every hour outside) and biological benefits of sleep still apply during this time, then a person can healthily stay conscious 24/7.
Being generous (and because it makes the numbers easier to handle), assuming that one typically sleeps for 8 hours a day, that means 1/3rd of a day is spent unconscious and thus not gaining new experiences or having time to think about the experiences they have. Five years in real time would have over eight years of experienced time, ten years would have over sixteen, and so on. Even at a 1/1 rate, you are effectively accelerating how many experiences you can obtain in a year while your body ages normally.
But if the dream reality had an accelerated time compared to the real world, such as 4 hours of dream time for every hour of real time, then things get weird. Still assuming eight hours of sleep a day, that eight hours that would be spent unconscious is replaced with 32 hours of experiences. Adding on the sixteen hours spent awake, you would effectively have two days of experience packed into one day.
And looking at it another way. If one normally spends 2/3rds of the day awake, then this "two days in one" situation means a person is awake for 6/3rds of a day (if that makes sense). Meaning they are actually experiencing 3 times as much as they would if they were unconscious while asleep. Five years of this would be the equivalent of fifteen years, ten years the same as thirty. Even while, biologically speaking, the body ages at the slow rate of one year every year.
With that in mind, what would happen when someone who isn't biologically mature goes through this? During this accelerated time where they never truly sleep, they can live, learn, and mature faster than their body would grow. For a child who starts the 24 hours in 24 hours situation when they were five years old, by age ten they would effectively have over thirteen years of life experience, by fifteen it would be over twenty. If they get the 48 hours in 24 instead, then by age ten they would have the life experience of a twenty-year-old. By fifteen they would be thirty-five.
Would their mental/psychological development go by just as fast? Probably not fully since there are biological elements that need to develop in real-time. I imagine it would be like a patchwork, where some areas and aspects of that child were more mature for their biological age in some areas while staying appropriate for their biological age in others. But I haven't a clue about those would be and I'd like to know.
Likewise, if an adolescent started doing this, what would it like for their mental/psychological development be like in these circumstances?