drugs modify brain structure

A recent study has shown that illegal drug addiction may be more than a mental issue. It is proven through research that these drugs actually changes the basic structure of one's brain. This change explains why it's so hard to quite. I believe the research is significant because it is one step closer to giving definitive answers to the so call "mental illness" characterized by quasi sciences such as Psychology. This research also indirectly explains smoker's dependency on cigeratte. In fact this research can be interpretted as a warning to taking any drugs, pharmasudical or illegal, as both of these substances can damage the brain.