Critics of zero tolerance policies also argue that the large numbers of students who are suspended and expelled from school experience negative effects which can prohibit them from finishing high school. Students who experience suspension, expulsion and arrests pay higher psychological and social costs: such as depression, suicidal thoughts, academic failure, and run the risk of being incarcerated as adults. In a study by Forrest et. al., (2000), psychologists identified that a third of youths in juvenile detention centers were diagnosed with depression shortly after being incarcerated. In addition to being diagnosed with depression many youths found themselves having suicidal thoughts (Gnau et. al. 1997).