"Addiction" properly refers to the compulsive use of a substance either for the pleasure derived from it, or to avoid the discomfort associated with its discontinuation. At least to start with there should be some pleasure in using the substance before one can become addicted to it. That is why the term is used in addictions to alcohol, cocaine, morphine, sleeping pills, etc. Motrin is a brand name for IBUPROFEN, an analgesic (pain killer). There is no pleasure in using it; hence no possibility of "addiction" per se. However, your friend may have a chronic headache which gets relieved temporarily with this medicine. This is similar to the situation of those taking insulin, blood pressure pills, anti-asthmatic pills, and so on. Next comes the issue of why he has this chronic headache. Daily pain killer is certainly not the right treatment for ANY headache. The cause of the headache should be found by a proper medical assessment. Looking at the long duration and the absence (in your report) of any other major symptoms, it is most likely to be TENSION HEADACHE, which can be due to several causes. Long-term use (and misuse) of pain killers can cause several complications, notably kidney damage. It is strongly to be recommended that your friend seek medical, and, if indicated, psychiatric assessment and treatment.