Seasonal affective disorder (SAD)

Overview

Melatonin (3 studies) shows mixed but potentially helpful signals for seasonal affective disorder at low daily doses (0.25–2 mg) over several weeks, though very short courses did not help. St. John's Wort (2 studies) reported symptom improvements in early uncontrolled trials. L-Tryptophan (1 study) appeared comparable to light therapy in a very small study.

Vitamin D (1 study) has insufficient evidence. Light therapy remains the best-supported treatment. See the heatmap and evidence reviews below.

Effect graph

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Relevant supplements

Relevant supplements sorted by DEX Score.


Melatonin	★★★★★	Low
Vitamin D	★★★★★	Low
St. John's Wort	★★★★★	Low
L-Tryptophan	★★★★★	Low

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Studies

Find individual evidence reviews for supplements sorted by DEX Score.

4 supplements for rated at least stars. All purchase bands. No minimum star filter.

MelatoninView supplement →

Reconsider purchase★★★★★

How we scored this

Effect SizeLowEvidenceMediumTrustMedium

Evidence Review

Some small studies show that taking low-dose melatonin (0.25 to 2 mg daily) for a few weeks may help reduce symptoms of winter depression (SAD). However, taking melatonin as a quick-dissolve tablet for just 6 days did not help. Differences in results might be due to how long melatonin was taken, how it was taken, or how severe symptoms were at the beginning. Light therapy is still the best-supported treatment.
Melatonin might help with winter depression if taken daily for a few weeks, but light therapy remains the main recommended treatment.

Browse 3 studies

RCTMelatonin treatment of winter depression following total sleep deprivation: waking EEG and mood correlates2005n=16

In 16 women with seasonal affective disorder after sleep deprivation, timed melatonin phase-advanced circadian rhythms and reduced sleepiness versus placebo.

Effect: No Benefit
Duration: 6 days
Dose: 0.5 mg/day
Population: Women
Participants: 16

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RCTEffect of controlled-release melatonin on sleep quality, mood, and quality of life in subjects with seasonal or weather-associated changes in mood and behaviour2003n=58

In 58 adults with subsyndromal seasonal affective disorder, sustained-release melatonin 2 mg for 3 weeks improved sleep quality and well-being versus placebo.

Effect: Benefit
Duration: 3 weeks
Dose: 2 mg/day
Population: Healthy adults
Participants: 58

View on PubMed

RCTMelatonin treatment of winter depression: a pilot study1998n=10

In 10 patients with winter depression, low-dose afternoon melatonin significantly reduced depression ratings versus placebo in a pilot study.

Effect: Benefit
Population: Patients with winter depression
Participants: 10

View on PubMed

L-TryptophanView supplement →

Reconsider purchase★★★★★

How we scored this

Effect SizeLowEvidenceLowTrustMedium

Evidence Review

A very small study found that taking L‑tryptophan (4–6 grams a day for 4 weeks) seemed to improve seasonal depression about as much as 2 weeks of light therapy.
However, the study was too small to know if there is a real difference between the two approaches.

Browse 1 study

RCTEfficacy of light versus tryptophan therapy in seasonal affective disorder1998n=11

In 13 SAD patients, light therapy for 2 weeks or tryptophan for 4 weeks each improved depression scores, with 31% responding to tryptophan.

Effect: Benefit
Duration: 4 weeks
Population: Patients with depressive disorders
Participants: 11

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St. John's WortView supplement →

Reconsider purchase★★★★★

How we scored this

Effect SizeLowEvidenceLowTrustMedium

Evidence Review

It isn't clear if taking St. John’s wort helps with seasonal affective disorder (SAD).
Early studies found that people taking St. John’s wort reported feeling better, with less anxiety, better sleep, and improved libido, whether used alone or with light therapy.
But these studies did not compare results with a placebo or control group.

Browse 2 studies

Clinical trialHypericum in seasonal affective disorder (SAD)1999n=168

In seasonal affective disorder, 168 patients taking Hypericum (Kira) for 8 weeks reported mean symptom scores falling from 21.3 to 13.0 versus baseline.

Duration: 8 weeks
Population: Adults with seasonal affective disorder
Participants: 168

View on PubMed

RCTHypericum in the treatment of seasonal affective disorders1994n=10

In seasonal affective disorder, Hypericum perforatum was comparable to light therapy for depressive symptom improvement in this controlled trial.