Insomnia is a common condition in which patients experience difficulty initiating sleep, maintaining sleep and/or wake earlier than desired. It can cause significant distress and impaired functioning.

Population surveys suggest that approximately 33% of the population experience at least one insomnia symptom, with only 1 in 10 seeking treatment. Female gender, older age, pain and psychological distress have all been associated with increased prevalence rates.

There is a strong association between insomnia and psychiatric disorders, such as depression, anxiety, and drug abuse. Rates of psychiatric comorbidity as high as 80% have been reported, with insomnia predating the onset of mood disorder in approximately half of cases. Insomnia has also been independently associated with increased healthcare utilisation, increased workplace injuries and absenteeism, and reductions in quality of life. A number of studies have demonstrated an association between insomnia and increased cardiovascular risk.