Defining Insomnia

Abstract

In the early 1980s, insomnia was thought to be a symptom, not a disorder. After two decades or more of sleep research and sleep medicine, insomnia is considered a distinct nosological entity. Perhaps what is different in the modern era is that initially the distinction between primary insomnia and secondary insomnia allowed for difficulty initiating and maintaining sleep to be both a disorder in its own right and symptom of other disorders, while the most recent international classification of sleep disorders divides up the category of insomnia into 11 diagnostic entities based on etiological and pathophysiological criteria. Thus, it is no longer either a symptom (secondary) or a diagnosis (primary) but both. This is a more accurate definition especially given the large proportion of insomniacs with comorbid medical conditions, the most common being psychiatric illnesses. We are fortunate to have several nosologies that recognize insomnia as a primary disorder. The various classification systems provide us the wherewithal to differentiate types of insomnia both by presenting complaint as well as by the factors that are thought to precipitate or perpetuate the illness.