Daytime fatigue

Daytime fatigue is a persistent lack of energy or motivation during waking hours, often paired with sleepiness, that interferes with work, mood and concentration.

Sleep medicine distinguishes fatigue, a feeling of exhaustion that does not necessarily lead to dozing, from excessive daytime sleepiness, a tendency to fall asleep in quiet situations; the two often overlap but point to different causes. Insufficient sleep, insomnia, sleep apnea, restless legs, shift work and circadian disruption are common sleep-related sources. Non-sleep causes include depression, anemia, thyroid disease, infections, chronic pain, medication side effects and the sedation that follows alcohol, antihistamines or cannabinoids taken the night before.

Assessment begins with a sleep history and diary and may include the Epworth Sleepiness Scale for sleepiness, fatigue-specific questionnaires, blood tests, and an overnight sleep study when apnea or narcolepsy is suspected. Addressing the underlying cause, keeping a regular sleep schedule and limiting sedating substances are the usual approaches. Daytime fatigue is also one of the most common side effects reported in cannabinoid clinical trials, listed as somnolence or fatigue, and next-day grogginess is a recognized concern with higher amounts of THC or cannabidiol taken at bedtime. Cannabinoids have been studied for sleep problems, but the evidence is limited, and no cannabinoid has an approved use for fatigue.