Ask HN: Have you experienced decline in problem-solving skills? How to improve?

I think this might actually be a few questions:

  1. Has anybody noticed their own cognitive decline? I'm 30 but am interested in experiences at all ages
  2. Does anybody have a good way of testing their intellect or problem-solving periodically? This would at least help me keep track going forward
  3. Has anybody found ways to improve their problem-solving skills? Or critical thinking?

I feel like my ability to solve problems well - efficiently, cleverly, satisfactorily, completely - has reduced over time (past year, maybe multiple years? I'm not really sure.) For example, I'll find that a programming solution didn't account for things I should've considered or introduced a new bug; or a co-worker will suggest a different solution and it seems obviously better. I don't think this has always been the case; I used to be pretty school smart in subjects like math and comp sci. My theories:

  - Maybe my intellect has diminished from using alcohol and weed at an early age?
  - Maybe that I've been feeling a bit burnt out
  - Maybe I've gotten lazy and rely too much on, e.g., stackoverflow
  - Maybe medicine I take for mental health?
  - Insufficient sleep? I've been getting 6-7 recently but should probably be getting 7-9
  - Maybe I've actually always been dumb and am only now realizing it!

Any thoughts would be appreciated. If it's something I can change, that would be a huge relief.