Mood disorders are among the most prevalent and disabling illnesses worldwide and can substantially interfere with daily functions. Mood disorders represent a spectrum of mood disturbances, from mania's significantly elevated mood to the remarkably low mood of depression. Depression is often characterized by symptoms such as hopelessness, sadness, irritability, guilt and cognitive impairments, like difficulty making decisions and poor concentration. Individual impacts on occupational performance vary greatly depending on the severity of symptoms, age of onset, number of episodes, responsiveness to treatment, co-occurring conditions. Depression can impair one's ability to care for personal health, such as following a healthy diet, eating well, exercising regularly, and sleeping. Previously maintained routines are often disrupted. Occupational therapists working within mental health can offer therapy and ongoing access to treatment and other supports to improve one's ability to maintain meaningful and productive roles. Occupational therapists strive to help clients experience a better quality of life through participation in occupations. Atchison, Ben, and Diane Dirette PhD. Conditions in Occupational Therapy: Effect on Occupational Performance. Wolters Kluwer/Lippincott Williams & Wilkins, 2012.