Mischa Barton's New Role

When I heard the news about Mischa Barton's arrest the other day I immediately thought that she was longing for her role in The O.C. and wanted to relive it in a new show called the OD - in reference to her being charged with drug possession.

Quite shocked to find out that she's only 21 as she appears to have been around forever. Never watched an episode of The O.C. myself. What possesses these young people to ruin themselves with drink and drugs?