February 7th 2020: Pathophysiology and Management of Insomnia

Defining Insomnia and its Pathophysiology:
  • Melatonin release is inhibited by blue light.  Note that white light (usual overhead lights contains blue light)
  • Insomnia: difficulty falling asleep (sleep initiation) or staying asleep (sleep maintenance) with consequence (symptoms)
  • Why do people get insomnia?  There are two competing forces in the brain.  Neurotransmitters that promote wakefulness (serotonin, norepinephrine, histamine, glutamate) and sleepiness (melatonin and adenosine)
  • Adenosine builds steadily during the day and is responsible for sleep initiation.  Melatonin is responsible for sleep maintenance rather than initiation.
  • Caffeine blocks adenosine receptors, which inhibits sleepiness
  • Often insomnia is more of an issue of excessive wakefulness, not inadequate sleepiness.  This is why a good history is important for identifying wakefulness triggers (stimulants, anxiety, light).
CBT for Insomnia
  • stimulus control: uses Pavlovian conditioning to restrict the bed for sleeping; the patient should be advised to get out of the bed after 20 minutes and do something distracting
  • sleep restriction: sleep deprivation is the best cure for insomnia; determine when the patient is falling asleep and tell the patient to go to sleep at that time while still waking at the same time (do not go lower than 6 hours to avoid adverse effects) 

Pharmacologic treatments for Insomnia

  • Classes of drugs for sleep: melatonin and melatonin receptor agonists, anti-histamine, anti-depressants, benzodiazepines, benzodiazepine receptor antagonists, anti-psychotics, orexin antagonists
  • if the patient has any component of anxiety start an SSRI first (sertraline and lexapro are good options as they are less activating)
  • Anti-depressants, mirtazepine and low-dose doxepin are sedating without being anti-cholinergic which makes them better than trazodone and amitriptyline
  • Benzodiazepine receptor agonists: Ambien, Lunesta and Sonata; these are better options than BZD’s; Sonata is shorter acting than Ambient and Lunesta
  • Avoid anti-psychotics for insomnia
  • Orexin antagonists: suvorexant and lemborexant (orexin deficiency causes narcolepsy)