Adolescents commonly experience problems such as attention deficit hyperactivity disorder, mood swings, low self-esteem, anxiety, depression, eating disorders, and substance abuse. Attention deficit hyperactivity disorder is a chronic problem with attention, hyperactivity, and impulsivity. Mood swings are emotional disturbances that affect physical, social, and cognitive processes. Low self-esteem refers to having a poor opinion of oneself. Anxiety disorders involve extreme worry and apprehension. Depression involves persistent sadness and loss of interest in activities. Eating disorders include anorexia nervosa and bulimia. Substance abuse refers to harmful use of alcohol and drugs.