For example, children who emigrated from another country at an early age may have a stronger tendency for developing this disorder, as they have already felt displaced from a location they were starting to become accustomed to. It is not uncommon for them to incessantly cling to their caregiver at first upon arrival to the new location, especially if the child is unfamiliar with the language of their new country. These symptoms may diminish or go away as the child becomes more accustomed to the new surroundings. Other sources note that a definite diagnosis of SAD should not be presented until after the age of three. Separation anxiety may be diagnosed as a disorder if the childs anxiety related to separation from the home or attachment figure is deemed excessive; if the level of anxiety surpasses that of the acceptable caliber for the childs developmental level and age; and if the anxiety negatively impacts the childs everyday life.Many psychological disorders begin to emerge during childhood. Nearly two-thirds of adults with psychological disorder show signs of their disorder earlier in life. However, not all psychological disorders are present before adulthood. In many cases, there are no signs during childhood.Behavioral inhibition (BI) plays a large role in many anxiety disorders, SAD included. Compared to children without it, children with BI demonstrate more signs of fear when experiencing a new stimulus, particularly those that are social in nature.
Adult separation anxiety disorder affects roughly 7% of adults. It has also been reported that the clinically anxious pediatric population are considerably larger. For example, according to Hammerness et al. (2008) SAD accounted for 49% of admissions.Research suggests that 4.1% of children will experience a clinical level of separation anxiety. Of that 4.1% it is calculated that nearly a third of all cases will persist into adulthood if left untreated. Research continues to explore the implications that early dispositions of SAD in childhood may serve as risk factors for the development of mental disorders throughout adolescence and adulthood. It is presumed that a much higher percentage of children suffer from a small amount of separation anxiety, and are not actually diagnosed. Multiple studies have found higher rates of SAD in girls than in boys, and that paternal absence may increase the chances of SAD in girls. See also
Homesickness
Stranger anxiety

References
External links
The Strange Situation: Window on a Childs Past and Future
Are you gonna leave me? Separation anxiety is associated with increased amygdala responsiveness and volume