Insomnia: impact on work, economics, and quality of life
In terms of clinical practice and of epidemiology, chronic insomnia is usually defined based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)9 or of the International Classification of Sleep Disorders (ICSD)10 which are:
• difficulty in falling asleep (sleep initiating insomnia), the occurrence of nocturnal awakenings with difficulties getting back to sleep (sleep maintenance insomnia), an early morning awakening (sleep offset insomnia), or a non-refreshing or non-restorative sleep, and often some combination thereof;
• at least three times a week for at least one month;
• insomnia produces clinically significant distress or impairment in social, occupational, or other important areas of daytime functioning.