Behavioral causes for conduct disorder (CD) activity may differ between boys and girls, aged 14-18 years. Symptoms of CD range from lying and truancy at one end to physical violence and weapon use at the other. Researchers at the University of Bath (UK) and other European universities used magnetic resonance imaging (MRI)-techniques to map the brains of over 200 teenagers aged 14 – 18 years. The study involved 96 young people with CD and 104 typically-developing young people. The brain’s prefrontal cortex is a region responsible for long-term planning, decision-making, and impulse control. This area was found to be thinner in boys and girls with CD compared to typically-developing boys and girls. Further, researchers found that young people with more severe forms of CD have more abnormal brain structure. As to differences between boys and girls, some brain areas showed lower cortical thickness in boys with CD, but higher thickess in girls with CD. The research highlights, for the first time, that there may be sex differences in the brain-based causes of CD.