Why Girls Cut themselves

Why girls cut themselves from Salon.com

Here's a summary of the study:The study actually found a weak correlation between mother-daughter conflict and self-mutilation; there was a stronger link between serotonin levels and cutting. "Most people think in terms of biology or environment rather than biology and environment working together," said Theodore Beauchaine, the study's coauthor. "Having a low level of serotonin is a biological vulnerability for self-harming behavior and that vulnerability increases remarkably when it is paired with maternal conflict."
It also raises the question why girls relationships with their fathers were not studied...could there be a bias behind this...the lets blame the mother bias?