Here is my take on it:
Addiction
1 : the quality or state of being addicted <addiction to reading>
2 : compulsive need for and use of a habit-forming substance (as heroin, nicotine, or alcohol) characterized by tolerance and by well-defined physiological symptoms upon withdrawal; broadly : persistent compulsive use of a substance known by the user to be harmful
Hobby
: a pursuit outside one's regular occupation engaged in especially for relaxation