The American Academy of Sleep Medicine (AASM; previously the American Sleep Disorders Association [ASDA]) classifies poor sleep hygiene-induced insomnia as one of the 13 extrinsic sleep disorders in the 1997 revised edition of the International Classification of Sleep Disorders (ICSD) (1). Inadequate sleep hygiene and extrinsic sleep disorders are those sleep disorders caused or maintained by forces outside the body, as opposed to intrinsic sleep disorders (e.g., narcolepsy, obstructive sleep apnea syndrome or psychophysiologic insomnia), which are conditions where the pathophysiology depends on factors within the body. In extrinsic sleep disorders, external factors are primarily responsible for producing the symptoms. Removal of these factors is the first step of treatment and almost always ameliorates if not completely resolves the disorder. Although the distinction between intrinsic and extrinsic sleep disorders is clear, the two may co-exist and/or interact in an individual patient. Volitional extrinsic factors may initiate the processes responsible for the development of some intrinsic sleep disorders, becoming internalized as the disorder develops. For example, psychophysiological insomnia can develop after years of extrinsic sleep-destroying habits collectively known as inadequate or poor sleep hygiene. Sleep hygiene refers to one’s engaging in a set of behaviors that are conducive to falling asleep and staying sleep and abstaining from behaviors that are not. For example, intake of caffeinated beverages very close to bedtime produces insomnia resulting from caffeine’s stimulating properties, thus constituting poor sleep hygiene. Setting aside relaxation or “down time” prior to going to bed facilitates sleep, therefore making it an element of good sleep hygiene.