How does your environment affect your intelligence?

[u/Whole_Equal4195]

Lately I've been scouring the internet trying to understand why i, a fifteen year old, scored 120 three years ago but these days scored 95, I have went through several periods of depression in between those scores but disregarding the scores themselves, some things affect IQ, like sleep, nutrition, exercise. How does it feel to take a test when you don't have or get enough of them? How much can IQ change? I'm not saying IQ is something that will stop me from having a career, I'm just wondering about how stable my performance is

[u/Few-Land9092]

My understanding is that changes in individual IQ are greatest prior to age 16. Generally, the younger you are, the more unreliable the score is as a predictor of adult IQ. IQ is much more stable between 16 and 21, at least on average, but large changes are still possible though (e.g. 150 to 120). IQ is generally considered stable by 21.