Multiple physical changes can impair the mental health of the aging individual. These changes include: acid-based imbalances, dehydration, electrolyte changes, hypothermia or hyperthermia, and hypothyroidism. This chapter reviews the most common mental health disorders affecting the elderly population and trends affecting care delivery. Moreover, chronic, unresolved pain has been associated with an increased risk of a mental health disorder such as depression, suicide, or anxiety. The aging individual may exhibit signs and symptoms of insomnia such as sleeping for short periods during the night, sleeping during times of normal social activities, arising early in the morning while others sleep, and experiencing daytime sleepiness. The chapter concludes by applying the nursing process from an interpersonal perspective to the care of an elderly patient with a mental health disorder.