Insomnia

Insomnia can be described as difficulty falling asleep at bedtime, waking up during the night several times or for a long time, and/or waking too early with inability to return to sleep:

• several organisations with interest in sleep disorders have put forward varying definitions of insomnia. All of these definitions share several key elements:
  • unsatisfactory sleep, either in terms of sleep onset, sleep maintenance or early waking
  • impaired daytime well-being and subjective abilities and functioning (1,2)

Insomnia was previously classified in several different ways, including primary (without a co-morbid condition) and secondary (associated with physical or psychiatric co-morbidities, drugs or substance abuse) (2). It was also sometimes divided according to the duration:

• chronic
  • presence of symptoms for at least three days a week (not necessarily every night) for at least 3 months
  • pre-sleep arousal (feeling sleepy before bed but then becoming more alert and unable to sleep once in bed) is common (3)
• acute
  • symptoms present for less than 3 months’ duration
  • most people will experience it at some point in any given year
  • usually caused by stress or change in the sleep pattern e.g. with travel, busy periods at work, illness, or emotional upset
    • once the trigger is removed sleep usually returns to normal (3)

However, the third edition of the International Classification of Sleep Disorder (4) states that insomnia should now be classified as:

Chronic insomnia disorder

• The sleep disturbances occur at least three times a week and have been present for the last 3 months.

Short-term insomnia disorder

• The sleep disturbances have been present for less than 3 months.

Other insomnia disorder

• Difficulty in initiating or maintaining sleep that does not meet the criteria of chronic insomnia or short-term insomnia disorder.

The 2019 publication of the British Association of Psychopharmacology Guidelines recommended that chronic insomnia disorder should be considered as a disorder in its own right. This means that "insomnia disorder should be diagnosed whenever insomnia diagnostic criteria are met, irrespective of any concurrent physical disorder or mental disorder, and also irrespective of any other concurrent sleep disorder" (1).

Insomnia (difficulty in either sleep initiation or maintenance at least once a week) affects around one-third of adults in Western countries. It affects 10-20% of the general population depending upon the defining criteria adopted:

• a higher incidence is seen in women and with increasing age
  • people over 65 show more sleep maintenance problems but a decrease in reported daytime problems compared with younger age groups (1)
• prevalence is between 1.5–2 times higher in women than in men (1)
• insomnia is a long-term disorder; many people have had insomnia for more than two years (1)
• approximately half of all diagnosed insomnia is comorbid with a psychiatric disorder (1)

There is at least a two-fold increased risk of subsequent depression and anxiety disorder in patients with pre-existing insomnia (1)

• insomnia has been associated with:
  • an increased risk of developing subsequent depression;
  • an increased duration of established depression; and
  • relapse following treatment for depression
    
    
• poor sleep quality also seems to correlate with high negative and low positive emotions, both in clinical and subclinical samples. Good sleep seems to be associated with high positive emotions, though not necessarily with low negative emotions

Insomnia is now recognised as reliably associated with mental health disorders including risk of depression and suicide, cardiovascular disease and type 2 diabetes (1):

• increased fatigue, impaired work productivity, reduced quality of life, and relationship dissatisfaction are also common in those with insomnia
  • such impaired functioning is an important driver for help-seeking behaviour (1)

References:

1. Wilson S et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders: An update. Journal of Psychopharmacology 2019, Vol. 33(8) 923 –947
2. The Royal Australian College of General Practitioners (RACGP) 2015. Prescribing drugs of dependence in general practice, Part B – Benzodiazepines
3. Cunnington D, Junge M. Chronic insomnia: diagnosis and non-pharmacological management. BMJ. 2016;355:i5819.
4. American Academy of Sleep Medicine. The AASM international classification of sleep disorders - third edition, text revision (ICSD-3-TR). Jun 2023 [internet publication].