Therapeutics of insomnia disorder

Abstract

“Insomnia” has come to a turning point globally. Firstly, a major change has been made to its nosology ; the distinction between “primary insomnia” and “secondary insomnia” has been discarded in the latest Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Classification of Sleep Disorders (ICSD), and they have been integrated as “insomnia disorder” as an independent diagnostic entity. This is based on the recognition that insomnia can have an independent course even with comorbid conditions, and also has a bidirectional relationship with them. The second major change is the global and ongoing transition of treatment priority from pharmacotherapy to cognitive behavioral therapy for insomnia (CBT–I). The accumulation of the broad range of evidence of CBT–I is striking, and most of the latest guidelines in western countries positioned CBT–I as the first–line treatment. It is also astonishing that it has been suggested that CBT–I can improve not only insomnia but also reduce or even prevent depression. Although its availability is a major issue, digital technology might be one of the solutions. The third major change is regarding the classes of hypnotics. Conventional benzodiazepine receptor agonists (BZRA) have become emphasized to be tapered or discontinued because of dependence and cognitive and motor side effects. Instead, melatonin receptor agonists and orexin receptor antagonists have been developed and focused, as for their reduced side effects like BZRA. The fourth potential major change might be emerged as to the insomnia subtyping. The latest ICSD also discarded conventional subtypes, such as psychophysiological insomnia or idiopathic insomnia, due to lack of stability in their diagnosis. Robust and practical subtyping covering predictability for depression or treatment response would be expected. Accordingly, further knowledge as to the pathophysiology of insomnia would also be needed.