well the way i look at it, it's quite simple.

70 hour week = too much work
too much work = very tired

sleeping during the day = not good sleep

not good sleep + very tired = body chemical imbalance
body chemical imbalance = depression, anxiety, etc!


also, if you are smoking before bed, and you wake up very tired, I have found that sleeping completely sober gives me a very refreshed feeling in the morning. On the other hand, if I can't get to bed at all, I'll take ONE medium sized hit from my bong (mids nothing special)... to the point where you can tell it's in your system, but you aren't really all that buzzed. At that point I conk out in about 5 minutes, and wake up fine. Better get 8 hours of hardly-stoned sleep then to get 6.5 hours of sober sleep...

...but it's better to get 8 hours sober sleep than 8 hours hardly-stoned sleep...