Risks of Nightly Diphenhydramine Use for Sleep
Lack of Efficacy
- The American Academy of Sleep Medicine recommends against using diphenhydramine for sleep due to its minimal efficacy, providing only 8-12 minutes of improvement over placebo, and no improvement in sleep quality 1, 2, 3
- Diphenhydramine reduces sleep latency by only 8 minutes compared to placebo and increases total sleep time by just 12 minutes, both falling well below thresholds for clinical significance 1, 2, 3
- Unlike effective sleep medications, diphenhydramine shows no improvement in subjective sleep quality compared to placebo 1, 2
- The sedative effects of antihistamines develop tolerance after just 3-4 days of continuous use, eliminating even the minimal short-term benefits 4, 5
Significant Anticholinergic Harms
- The antimuscarinic effects of diphenhydramine create multiple serious risks, including central nervous system impairment, causing delirium, slowed comprehension, cognitive impairment, and daytime sedation 6
- Diphenhydramine impairs vision, causes urinary retention, and worsens constipation 6
- The combination of sedation, cognitive impairment, and impaired coordination significantly increases fall risk, especially in older adults 6
- The 2019 Beers Criteria carry a strong recommendation to avoid antihistamines in older adults due to their antimuscarinic adverse effect profile 4, 5
Guideline Recommendations
- The American Academy of Sleep Medicine issues a weak recommendation suggesting clinicians not use diphenhydramine for treating sleep onset or sleep maintenance insomnia, based on the absence of clinically significant improvement 3
- The VA/DoD Guidelines advise against the use of antihistamines for chronic insomnia disorder, noting that no studies met inclusion criteria for their use as interventions, and tolerance develops within days 4, 5