People who are tormented by bullying are at increased risk for mental health problems, including depression and anxiety. Studies have linked racial harassment to psychological strain, depression, and nervousness. Those who are tormented by bullying, harassment and intimidation are also at increased risk for developing low self-confidence, and a variety of negative academic outcomes including having a decreased ability to concentrate, poor grades, and irregular class attendance. Bullying also contributes to the likelihood of committing suicide. While bullying among peers tends to peak in middle school, it remains common among college and university students. North American males and females experience verbal, physical, and social bullying at similar rates while attending post-secondary institutions, and nearly 25% of undergraduate students say they have been bullied at least once or twice.