1. Psychological disorders are defined as abnormalities of the mind that cause persistent behaviors affecting daily function. They include mood disorders, personality disorders, anxiety disorders, and eating disorders.
2. Causes are unknown but may include childhood experiences, chemical imbalances, illnesses, heredity, stress, and prenatal exposures. Disorders can be serious and life-threatening.
3. Obsessive-compulsive disorder is characterized by obsessive thoughts and compulsive rituals performed to relieve anxiety. Low serotonin levels and environmental stressors may contribute to its development.