Insomnia – Neurobiology | Pathophysiology | Assessment and Management
Time to read: 9 minutes
Insomnia is defined as an on-going subjective dissatisfaction of the duration or quality of sleep .
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 followup with only 27% experiencing spontaneous resolution and 21% experienced remission and relapse.
Although insomnia can often spontaneously remit, it is often chronic with a median duration of 3 years reported. 
It is more common in women than men, which may be due to differences in sex steroids. 
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. 
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 development of depression in subsequent years by two times and also 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.).