Dissatisfaction with overnight sleep is such a common complaint that it is often overlooked or, at best, incompletely assessed. Indeed, if specifically asked about sleep quality, approximately one-third of those visiting a general practitioner will report problems, a proportion that rises to two-thirds of those attending psychiatry services. Insomnia is reported more in females and generally increases with age.

Transient or short-term insomnia, usually triggered by a recognisable life event or stressor, is a universally recognised phenomenon. However, the underlying mechanisms or causes of chronic insomnia are often more obscure. Furthermore, the pathways for managing significant insomnia presenting to primary care are generally very poorly developed, creating frustration for patients and physicians alike.

Defining chronic insomnia as a formal sleep disorder is challenging, especially as it is a heterogeneous complaint. Broadly, subjects can report difficulty with any aspect of sleep, whether it is initiation, duration, consolidation or quality. The problem persists despite a desire to sleep normally with adequate time and opportunity for satisfactory sleep.

Most authorities would suggest an approximate benchmark of 30 minutes either trying to achieve sleep or a similar time spent awake after sleep onset as reflecting significant insomnia. The problem needs to have been present most nights of the week for over one month and, importantly, to have resulted in a degree of daytime impairment. Typical daytime symptoms include lethargy, malaise and cognitive blunting, especially in tasks involving attention or concentration. In severe cases, the problem completely dominates a subject’s life such that vocational, social or school performance is severely compromised.

Importantly, insomnia is recognised as a reliable independent risk factor for developing depression and hypertension. Furthermore, numerous somatic symptoms, such as increased muscle tension, gastrointestinal upset and headache, are often intimately associated with insomnia.

Although the distinction may often be blurred, it is useful to consider insomnia either as a primary phenomenon, reflecting an intrinsic sleep disorder, or as having an extrinsic cause largely due to factors such as the environment, drugs or other medical conditions. Broadly speaking, an important clue that insomnia is a primary rather than a co-morbid phenomenon is that subjects report a complete inability to nap under any circumstances during the day, despite persistently restricted or poor quality nocturnal sleep. At its simplest, a subject with primary insomnia can be considered ‘tired but wired’.

Mechanisms of insomnia

Insomniacs will often lose confidence that they can fall asleep in their bedrooms by a process of negative conditioning. Such patients will report significant sleepiness late evening whilst relaxing in the living room which disappears immediately they enter the bedroom. The failure of the bedroom to cue sleep occurs particularly in those who habitually use the room for activities such as studying or paying bills, for example. Paradoxically, compared to good sleepers, subjects with this type of insomnia generally spend an inordinate large amount of time in the bedroom across 24 hours but a much smaller proportion of it actually asleep (Figure 5.1).

Figure 5.1 Graph demonstrating the average time a group of typical insomniacs spends in bed (around nine hours) compared to time asleep (6.5 hours). This contrasts with good sleepers who spend 8.5 hours in bed, 7.5 hours of which are estimated asleep.