When I was in the third or fourth grade, I had an extreme form of this type of depression that lasted for maybe a year or longer. Instead of just reflecting on the meaning of life, I worried reality might not be real and understood even then at my young age there's no way to prove the people around me weren't constructs of my imagination. I came to these conclusions independently without ever hearing of Brain in a Vat, Evil Genius, or watching The Matrix, and it was very terrifying back then.

As I've grown up, I still realize there's no way to prove the world around me is real, but I'm glad I encountered this theory so young because I've had a good while to be motivated by the fact that it doesn't matter if it isn't real. What matters is what I do with this experience and how much joy I get out of it.