A new government study suggests that teens who smoke marijuana to "self-medicate" may worsen their underlying depression or other mental health issues. The report is based on a number of studies linking teen marijuana use and mental health issues. Other experts say the report's findings are misleading, citing that substance abuse and depression are already linked by genetic and environmental factors and that many teens who use drugs also have clinical depression. But both sides stress say parents should be aware of depression signs in teens, particularly if they suspect drug use.