What Drug Addiction Could This Be?

1. Money spent on drug – $3,000 – $4,000 a month

2. Sleeping irregular hours and sleeping long periods of time

3. Lot of weight gain

4. Laziness and low motivation

5. Still able to hold a 40 hour per week job

….what drug addiction would fit this description?
There are no needle marks on this person’s arm
what type of pills?