Question

which action constitutes substance abuse?
use of psychological medications
use of medication belonging to someone else
use of fortified \power\ drinks
use of caffeine

Explanation:

Substance abuse involves using a substance in a way that is not intended or prescribed. Using medication belonging to someone else is not the proper or legal use of that substance. Psychological medications can be used appropriately under a doctor's supervision. Fortified "power" drinks and caffeine, while they can have negative effects if over - used, are not typically considered substance abuse in the same way as using someone else's medication without authorization.

Answer:

use of medication belonging to someone else