I was much smarter before having depression. The reason? I used to be interested in a lot of different things, reading about them, trying them out. Now it’s just like why bother, makes no difference anyway.
I am convinced that “intelligence” or “intellect” or however you want to brand it is just a measurement of interest in a topic, nothing else.
There’s a social aspect to cognition I’ve noticed recently. Between depression and a recent bout of unemployment, I’ve been a lot less social and noticed my language faculties suffering. It’s harder to remember less frequently used words and it takes me longer to assemble statements. This makes me feel like I’m sometimes drifting in a fog and it’s more difficult to focus. Language is a large part of how we assemble our understanding of and interact with the world and it makes me feel less intelligent when I’m slow to assemble a thought or have to look up a definition to find the word I’m trying to use.
Although, the feeling that I’m slower with my language does not necessarily indicate cognitive decline. This is only a personal observation