Answer:
reason #1: They do drugs because they want to fit in just like their friends.
reason #2: To fix a problem in their life so they try doing drugs to see if it helps
reason #3: They use it is they are stress or peer pressure to do it.
reason #4: They might be heartbroken from a relationship they just ended so they go to the next thing which is drugs.
reason #5: Lastly but not least they want to relax so they try to do drugs to relax themselves.
Explanation: Hope this helps :)