Can green‑light therapy be used safely as an adjunctive treatment for adults with episodic or chronic migraine who do not have photosensitive epilepsy?

Green Light Therapy for Migraine

Green light therapy can be safely used as an adjunctive treatment for adults with episodic or chronic migraine who do not have photosensitive epilepsy, based on emerging evidence showing significant reductions in headache frequency and intensity without reported adverse effects.

Evidence Base and Efficacy

Primary Outcomes in Clinical Trials

• A prospective one-way crossover trial (n=29) demonstrated that green light-emitting diode (LED) exposure for 1-2 hours daily significantly reduced headache days from 7.9 to 2.4 days per month in episodic migraine patients and from 22.3 to 9.4 days per month in chronic migraine patients after 10 weeks of treatment 1

• The same trial showed that white LED exposure produced minimal benefit (18.2 to 16.5 headache days), while green LED therapy achieved substantially greater magnitude of improvement across multiple quality-of-life measures including the Headache Impact Test-6 and Five-level EuroQol survey 1

• A large real-world observational study (n=181 completers from 698 enrolled) found that green light improved headache in 55% of all 3,232 treated attacks, with 61% of participants classified as responders (≥50% improvement rate) and 42% as super-responders (≥75% improvement rate) 2

Secondary Benefits Beyond Pain Relief

• Green light therapy improved photophobia in 53% of all attacks (68% in responders), reduced anxiety in 34% of attacks (46% in responders), and enhanced same-night sleep quality in 49% of attacks (59% in responders) 2

• These improvements in photophobia, anxiety, and sleep may be secondary to headache relief itself, though the mechanism remains under investigation 2

• A case report of a colorblind patient (protanomaly) demonstrated significant decreases in headache pain intensity with green light exposure, suggesting the analgesic effect is mediated through non-image-forming intrinsically photosensitive retinal ganglion cells rather than cone photoreceptors 3

Safety Profile

• No adverse events or side effects were reported in any of the clinical trials evaluating green light therapy 1, 4

• The absence of reported side effects across multiple studies indicates green light therapy has a favorable safety profile compared to pharmacological interventions 4

• Green light therapy does not carry the risks associated with medication overuse headache, dependency, or systemic adverse effects that limit pharmacological options 1

Clinical Implementation Algorithm

Patient Selection Criteria

• Green light therapy is appropriate for adults with episodic migraine (1-14 headache days per month) or chronic migraine (≥15 headache days per month) who prefer non-pharmacological approaches or wish to complement existing pharmacological treatments 1, 4

• The therapy can be considered for patients who have failed or cannot tolerate standard preventive medications, though it should not replace evidence-based first-line pharmacological treatments 1

• Patients with photosensitive epilepsy should be excluded due to theoretical seizure risk, though no cases have been reported in migraine trials 1

Treatment Protocol

• Prescribe daily exposure to narrow-band green LED light (wavelength approximately 520-530 nm) for 1-2 hours during the interictal period (between attacks) as the primary preventive protocol 1

• For acute treatment during migraine attacks, patients may use green light exposure for approximately 2 hours, which has been associated with relief of pain and photophobia in real-world use 2

• The therapeutic effect requires consistent daily exposure for 10 weeks before assessing efficacy, as demonstrated in the crossover trial 1

• Patients should continue their current acute and preventive migraine therapies while initiating green light therapy, as the intervention is intended as adjunctive rather than replacement treatment 1

Expected Timeline and Response Assessment

• Evaluate response after 10 weeks of consistent daily exposure by comparing headache frequency (days per month) and intensity using validated tools such as the Headache Impact Test-6 1

• Define treatment success as ≥50% reduction in headache days per month (responder) or ≥75% reduction (super-responder), consistent with standard migraine preventive therapy endpoints 2

• Approximately 39% of patients may be non-responders (<50% improvement), and these individuals should continue evidence-based pharmacological preventive therapy without relying on green light as monotherapy 2

Position Within Comprehensive Migraine Management

Integration With Pharmacological Treatment

• Green light therapy does not appear in the 2025 American College of Physicians guidelines for episodic migraine prevention, which prioritize pharmacological monotherapy including beta-blockers, antiseizure medications, CGRP antagonists, and tricyclic antidepressants 5

• Green light therapy should be positioned as a complementary non-pharmacological intervention rather than a replacement for guideline-recommended first-line preventive medications such as propranolol 80-240 mg/day, topiramate, or CGRP monoclonal antibodies 5

• Patients using green light therapy must still adhere to the critical frequency limitation of acute migraine medications (≤2 days per week) to prevent medication-overuse headache 5

Advantages Over Other Non-Pharmacological Approaches

• Green light therapy has more robust clinical trial evidence (including a prospective crossover trial) compared to other non-pharmacological interventions such as acupuncture, biofeedback, or nutraceuticals like riboflavin, which have limited or inconsistent evidence 1, 4

• The therapy requires no specialized training, has no systemic absorption, and can be self-administered at home, offering practical advantages over clinic-based interventions 1

Critical Limitations and Caveats

Evidence Quality Concerns

• The current evidence base consists of small sample sizes (largest trial n=29 completers), open-label designs without blinded controls, and observational real-world data that cannot establish causation 1, 2, 4

• The one-way crossover design of the primary trial introduces potential bias, as patients were not randomized and all received white light before green light, allowing for temporal confounding and placebo effects 1

• The 26% completion rate in the real-world diary study (181 of 698 enrolled) raises concerns about selection bias and generalizability 2

• Larger randomized, double-blind, placebo-controlled trials are urgently needed to confirm efficacy and establish green light therapy as an evidence-based treatment option 4, 1

Practical Implementation Barriers

• The requirement for 1-2 hours of daily light exposure may be burdensome for patients with demanding work schedules or caregiving responsibilities 1

• The specific wavelength and intensity of green LED devices used in clinical trials are not standardized, and commercially available devices may vary in therapeutic efficacy 2, 1

• Insurance coverage for green light devices is unlikely given the preliminary evidence base, creating potential cost barriers for patients 1

Clinical Pitfalls to Avoid

• Do not recommend green light therapy as monotherapy for patients who meet criteria for pharmacological preventive treatment (≥2 attacks per month with ≥3 days of disability, or acute medication use >2 days per week), as this delays evidence-based care 5

• Do not allow patients to increase frequency of acute medication use while waiting for green light therapy to take effect, as this creates risk of medication-overuse headache 5

• Do not present green light therapy as a proven alternative to guideline-recommended treatments; instead, frame it as an investigational adjunctive option with preliminary positive data but limited high-quality evidence 4, 1

• Ensure patients understand that the 10-week trial period is necessary before assessing efficacy, and that approximately 40% of users may not experience meaningful benefit 2, 1