Insomnia

Definition

Insomnia is a sleep disorder characterized by difficulty initiating or maintaining sleep, or non-restorative sleep, leading to impaired daytime functioning and distress.

Epidemiology

• Prevalence ranges from 10–30% in adults, lower in children
• Chronic insomnia affects 6–10% of the population
• More common in women and older adults
• Often comorbid with psychiatric disorders such as depression and anxiety
• Associated with significant impact on quality of life and productivity

Etiology

• Primary insomnia: idiopathic or psychophysiological
• Secondary insomnia: due to medical conditions (pain, respiratory disorders, neurological diseases)
• Psychiatric disorders: depression, anxiety, PTSD
• Medications: stimulants, corticosteroids, some antidepressants
• Substance use: caffeine, alcohol, nicotine
• Environmental factors: noise, light, shift work
• Behavioral factors: irregular sleep schedule, poor sleep hygiene

Pathophysiology

• Hyperarousal of the central nervous system
• Dysregulation of circadian rhythms
• Altered activity in hypothalamic-pituitary-adrenal axis leading to increased cortisol
• Imbalance in neurotransmitters regulating sleep (GABA, serotonin, orexin)
• Neurobiological and genetic susceptibility
• Cognitive factors: racing thoughts, anxiety about sleep
• Feedback loops between insomnia and psychiatric disorders