A n adjustment disorder is a condition of subjective emotional distress, typically involving depression, anxiety, or both, that follows a significant life change or stressful life event that interferes with a person's ability to function effectively. Because many older adults contend with life issues to which they are challenged to adjust, this chapter on adjustment reaction disorder focuses on this age group.Each day about 10,000 members of the so-called baby boomer generation turn 65 years of age. By 2030, about 20% of the U.S. population will be 65 years of age or older (Karel, Gatz, & Smyer, 2012). Many European nations and Japan will also have historically high proportions of older adults. Surprisingly to many, the rates of almost all mental disorders, including depression, are lower in older adults than in younger adults. Furthermore, surveys show that older adults are happier than younger adults (Carstensen, Fung, & Charles, 2003). The one mental disorder that is more common in older versus younger adults is dementia, a progressive loss of mental abilities. The most common ICD-10-CM mental disorders related to cognitive decline in older adults are Alzheimer's disease (G30.0 and F02.8) and Vascular dementia (F01.5).Among older people seeking psychological services, depression and anxiety are frequently expressed concerns. Often depression or anxiety is preceded