their ability to regulate their emotions and adjust to novelty. Cross-cultural research, with populations as diverse as refugees and boarding school students, suggests considerable agreement on the definition of homesickness. Additional historical perspectives on homesickness and place attachment can be found in books by van Tilburg & Vingerhoets, Matt, and Williams. Diagnosis and epidemiology Whereas separation anxiety disorder is characterized by "inappropriate and excessive fear or anxiety concerning separation from those to whom the individual is attached" symptoms of homesickness are most prominent after a separation and include both depression and anxiety. In DSM terms, homesickness may be related to separation anxiety disorder, but it is perhaps best categorized as either an adjustment disorder with mixed anxiety and depressed mood (309.28) or, for immigrants and foreign students as a V62.4, Acculturation Difficulty. As noted above, researchers use the following definition: "Homesickness is the distress or impairment caused by an actual or anticipated separation from home. Its cognitive hallmark is preoccupying thoughts of home and attachment objects." Recent pathogenic models support the possibility that homesickness reflects both insecure attachment and a variety of emotional and cognitive vulnerabilities, such as little previous experience away from home and negative attitudes about the novel environment. The prevalence of homesickness varies and depends on the population studied and the way homesickness is measured. One way to conceptualize homesickness prevalence is as a function of severity. Nearly all people miss something about home when they are away, so the absolute prevalence of homesickness is close to 100%, mostly in a mild form. Roughly 20% of university students and children at summer camp rate themselves at or above the midpoint on numerical rating scales of homesickness severity. 5–7% of students and campers report intense homesickness associated with severe symptoms of anxiety and depression. In adverse or painful environments, such as the hospital or the battlefield, intense homesickness is far more prevalent. In one study, 50% of children scored themselves at or above the midpoint on a numerical homesickness intensity scale (compared to 20% of children at summer camp). Soldiers report even more intense homesickness, sometimes to the point of suicidal misery. Aversive environmental elements, such as the trauma associated with war, exacerbate homesickness and other mental health problems. Homesickness is a normative pathology that can take on clinical relevance in its moderate and severe forms. Risk and protective factors Risk factors (constructs which increase the likelihood or