As per the title, I'm wondering what benefits there are for someone who doesn't abuse these substances but would imbibe weekly. Some weekends I do neither, most I would smoke on a Saturday night. Maybe have 3-4 drinks. It's been like that for years.

I'm 31 now. I did a tonne of drugs when I was 19-23 - acid, pills, downers, uppers, coke, you name it. Quit all that and stuck with alcohol/cannabis, which eventually became more moderate over time.

I'm concerned about potential brain damage I've inflicted or could be continuing even with this level of use. Is there a "safe" or reasonable level that doesn't result in the degeneration associated with these substances?

I'm currently doing a dry January and enjoying the extra space, time, and energy. It's mild, but a noticeable improvement. If I kept this up permanently, could there be greater benefits like improved memory, clarity, perceptiveness, maybe even intelligence (open to interpretation on that one)?