Insomnia – Neurobiology | Pathophysiology | Assessment and Management
According to the DSM-V, the following are the key criteria for insomnia:
- Predominant complaint of dissatisfaction with sleep quantity or quality associated with difficulty initiating sleep, difficulty maintaining sleep and early morning awakening with an inability to return to sleep.
- The sleep difficulty occurs at least three nights per week, and the difficulty is present for at least three months.
The prevalence of insomnia is approximately 30% to 35% and using the DSM-V criteria, the prevalence is approximately 10% and multinational studies.
A longitudinal study of 388 people found that 46% had ongoing symptoms and met the diagnosis criteria for insomnia disorder after three years of follow-up. However, only 27% experienced spontaneous resolution, and 21% experienced remission and relapse.
It is more common in women than men, which may be due to differences in sex steroids. [Johnson E et al., 2006]
There are also potential race and ethnic differences; however, data is inconsistent; however, what is known is that it is often co-morbid with a psychiatric disorder. [Franzen P et al., 2008]
Humans spend approximately one-third of their life sleeping. A primary function of sleep appears to be the activation of the glymphatic system to promote the efficient elimination of neurotoxic waste products (e.g β-amyloid) produced during wakefulness. The glymphatic system also facilitates the brain-wide distribution of several compounds, including glucose, lipids, amino acids, growth factors, and neuromodulators. [Jessen et al., 2015].
Even one night of total sleep deprivation impairs molecular clearance from the human brain, and that humans do not catch up on lost sleep. [Eide et al., 2021]
Sleep restores synaptic plasticity, with beneficial effects on learning processes, while sleep deprivation induces alteration in LTP/LTD mechanisms, increases cortical excitability, and negatively impacts learning. [Gorgoni et al., 2013]
Quality of life is deeply affected by insomnia due to the associated neuropsychiatric sequelae, including impairment of cognition, mood, and functionality.
Insomnia increases the risk of developing depression in subsequent years by two times and has a bidirectional relationship with anxiety disorders.
Besides, insomnia is associated with a dysfunctional immune system. Not surprisingly, insomnia is also associated with an increased risk of mortality (depression, cardiovascular disease, accidents, etc.). [Taylor D et al., 2003]