Bullying involves unwanted aggressive behavior among school-aged children that involves a real or perceived power imbalance and is repeated over time. Both bullies and victims may experience lasting problems. Causes of bullying include lack of attention, wanting power over peers, problems at home, seeing bullying as cool, aggressive personalities, lack of supervision, jealousy, revenge, and taking out feelings on others. Effects of bullying include depression, suicidal thoughts, abnormal fears, sleep disorders, nervous habits, frequent crying, poor appetite, school problems, and rage.