Insomnia disorder (difficulty sleeping despite optimum conditions with daytime impairment, which cannot be explained by another sleep disorder) must be differentiated from other diseases that cause difficulty sleeping such as normal variants (short sleeper, excessive time in bed), circadian rhythm sleep disorders, obstructive sleep apnea, movement disorders, narcolepsy, and substance/medication-induced sleep disturbances.

Insomnia disorder (difficulty sleeping despite optimum conditions with daytime impairment, which cannot be explained by another sleep disorder) must be differentiated from other diseases that cause difficulty sleeping (because the treatment guidelines are prepared for the people who meets the criteria for insomnia disorder rather than other diseases with insomnia symptoms) such as:^[1]

• Normal variants
  • Short sleeper (needs <6 h of sleep)
  • Excessive time in bed
• Sleep disorders
  • Circadian rhythm sleep disorder
    • Jet lag
    • Delayed sleep–wake phase disorder (night owl)
    • Advanced sleep–wake phase disorder (early bird or lark)
    • Shift work sleep disorder
    • Non-24-hour sleep-wake syndrome
    • Irregular sleep–wake rhythm disorder
  • Obstructive sleep apnea
  • Movement disorders
    • Restless legs syndrome
    • Periodic limb movement disorder
  • Narcolepsy
• Substance/medication-induced sleep disturbances^[2]