Health Highlights: Sept. 7, 2004 Here are some of the latest health and medical news developments, compiled by editors of HealthDay:    ------      Early Puberty Increases Risk of Substance Abuse      Youngsters who begin puberty at an early age are more likely to experiment with and abuse alcohol, tobacco, and marijuana than kids who start puberty at a later age, says a Australian study in the September issue of the journal Pediatrics.      The study found that early puberty was more important than school grade or age in influencing this kind of behavior...