Does vitamin B1 help with anxiety?

There is no good evidence that it does. Nobody has pooled trials of vitamin B1 alone for anxiety. A 2019 meta-analysis of B-vitamin supplements, each with at least three B vitamins, found no effect on anxiety in 562 people (SMD 0.03, 95% CI -0.13 to 0.20). The one randomized trial built around anxiety gave 43 young adults 100 mg of B1 with 100 mg of B2 for four weeks, and it did not lower anxiety more than placebo (adjusted p = 0.36).

Unsettled. The question is open because it has barely been asked. Every pooled result tests B1 inside a mixture, and the trials of thiamine on its own are small and mostly measured depression, mood or well-being instead of anxiety. One registered trial of thiamine for anxiety is now recruiting.

What the trials found

B vitamins and multivitamins together

The 2019 meta-analysis covered trials of daily supplements with three or more B vitamins for at least four weeks. Anxiety did not move. Stress improved slightly (SMD 0.23), and depression did not reach significance (SMD 0.15, 95% CI -0.01 to 0.32). A 2013 meta-analysis of eight trials of multivitamin and mineral formulas, taken for at least 28 days by healthy people, found a small drop in anxiety (SMD 0.32, 95% CI 0.16 to 0.48). Those formulas held many ingredients, and the share due to thiamine cannot be separated.

The trial that measured anxiety

In the four-week trial of B1 with B2 in 43 Chinese students with raised anxiety scores, the supplement group ended marginally lower on anxiety, a difference that did not reach significance. Their perceived stress fell from 21.5 to 15.5, against 20.3 to 19.8 on placebo. It was small and short, and riboflavin was in the same capsule.

Thiamine alone, on other outcomes

In 51 inpatients with major depression on an SSRI, adding thiamine improved depression faster than placebo by week 6, and the difference was no longer significant at week 12. In 80 elderly Irish women with marginal thiamine status, 10 mg a day for six weeks raised general well-being and appetite and lowered fatigue. In 66 hospitalized patients in a manic episode on lithium, 100 mg of B1 did not improve mood more than placebo, while B6 did.

In a six-month trial of 600 mg a day of benfotiamine, a synthetic form of thiamine, men with severe alcohol use disorder saw phobic anxiety scores fall by 0.98 against 0.12 on placebo. That came from a subgroup of a trial designed for drinking outcomes, and in men with milder disease placebo did better on anxiety. In 120 young women, 50 mg a day for two months raised thiamine status, and that rise went with feeling more clearheaded, composed and energetic, in a controlled trial whose abstract does not say it was randomized.

Diet and depression

A 2022 meta-analysis of observational studies linked the highest dietary B1 intake with 31 percent lower risk of depression than the lowest (RR 0.69). Dietary B1 tracks overall diet quality. In US NHANES adults the link held only below about 1.35 mg a day (OR 0.68) and was absent above it, which fits no extra benefit once intake is adequate. Neither study measured anxiety.

Who should be careful

NIH reports no adverse effects from high thiamine intakes. The cautions are mostly about who runs short of it.

Not for everyone. NIH has set no upper limit for thiamine, because no adverse effects have been reported at intakes of 50 mg a day or more, and that is an absence of reports rather than proof of safety at any dose. The diuretic furosemide is linked to thiamine loss in urine, possibly to deficient levels. Case reports describe beriberi or Wernicke's encephalopathy during treatment with the cancer drug fluorouracil. Up to 80 percent of people with chronic alcoholism develop thiamine deficiency. If you drink heavily or take either drug, low thiamine is a question for your doctor, and anxiety is no reason to self-treat it.

What expert bodies say

The NIH Office of Dietary Supplements lists confusion, short-term memory loss and other mental signs among the early signs of thiamine deficiency. Its fact sheet does not name anxiety. We found no guideline that recommends thiamine for anxiety.

How we searched

What would change this answer

• The trial now recruiting (NCT06322212), which compares thiamine with placebo with anxiety as the main outcome in adults with type 2 diabetes. It is the first of its kind we found, and it has no results yet.
• A trial of thiamine alone in people with an anxiety disorder diagnosis. None exists.
• A trial that selects people with low thiamine status, since several of the signals that exist come from people who drink heavily or have marginal status.

Sources

1. ev-thax-01 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 18 articles (16 trials, 2015 participants); anxiety n = 562
   A benefit to depressive symptoms did not reach significance (n = 568, SMD = 0.15, 95% CI = -0.01, 0.32, p = 0.07), and there was no effect on anxiety (n = 562, SMD = 0.03, 95% CI = -0.13, 0.20, p = 0.71).
   
   Who: healthy and at-risk adults in RCTs of daily supplementation with three or more B vitamins for at least four weeks
   Effect: anxiety SMD 0.03 (95% CI -0.13 to 0.20); stress SMD 0.23 (0.02-0.45); depression SMD 0.15 (-0.01 to 0.32)
   Certainty: B-complex products, not thiamine alone.
   Nutrients, 2019 · checked 2026-10-07 · we read the abstract
2. ev-thax-02 · Meta-analysis or systematic review · meta-analysis of RCTs · n = 8 studies
   Supplementation reduced the levels of perceived stress (standard mean difference [SMD]=0.35; 95% confidence interval [CI]=0.47-0.22; p=.001), mild psychiatric symptoms (SMD=0.30; 95% CI=0.43-0.18; p=.001), and anxiety (SMD=0.32; 95% CI=0.48-0.16; p<.001), but not depression (SMD=0.20; 95% CI=0.42-0.030; p<.089).
   
   Who: nonclinical general-population samples, multivitamin/mineral supplements vs placebo for at least 28 days
   Effect: anxiety SMD 0.32 (95% CI 0.16-0.48); perceived stress SMD 0.35; depression not significant
   Certainty: Multi-ingredient formulas; the thiamine share cannot be isolated.
   Psychosom Med, 2013 · checked 2026-10-07 · we read the abstract
3. ev-thax-03 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial · n = 43
   Although the supplementation group had marginally lower anxiety scores than the placebo group at week 4, the between-group difference did not reach statistical significance (adjusted p = 0.36) after adjusting for baseline SAS scores.
   
   Who: Chinese students 18-25 years with Self-Rating Anxiety Scale score above 44, without generalized anxiety disorder; 100 mg B1 + 100 mg B2 daily vs placebo
   Effect: no between-group difference in SAS anxiety score at week 4 (adjusted p = 0.36)
   Certainty: Small, short; B1 combined with B2.
   Nutrients, 2025 · checked 2026-10-07 · we read the fulltext
4. ev-thax-04 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial · n = 43
   The PSS scores decreased significantly in the supplement group from 21.5 ± 4.1 to 15.5 ± 4.5 (p < 0.05), while the placebo group showed a change from 20.3 ± 4.3 to 19.8 ± 5.5.
   
   Who: young adults with elevated anxiety; 100 mg B1 + 100 mg B2 vs placebo for four weeks
   Effect: PSS 21.5 to 15.5 (p < 0.05) vs placebo 20.3 to 19.8
   Certainty: Stress, not anxiety; small sample.
   Nutrients, 2025 · checked 2026-10-07 · we read the abstract
5. ev-thax-05 · Randomized controlled trial(s) · randomized placebo-controlled trial · n = 51
   Compared to placebo, adjuvant thiamine improved symptoms of depression after 6 week of treatment, and improvements remained fairly stable until the end of the study, though mean differences at week 12 were not statistically significant anymore.
   
   Who: inpatients with MDD (HDRS above 24), mean age 35.2, standardized SSRI plus thiamine or placebo
   Effect: faster HDRS improvement at week 6; week 12 difference not significant
   Certainty: Depression outcome, adjunct to SSRI; dose not given in abstract (no PMC copy).
   Eur Arch Psychiatry Clin Neurosci, 2016 · checked 2026-10-07 · we read the abstract
6. ev-thax-06 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial (secondary analysis) · n = 85 randomized, 50 completed
   A statistically significant reduction in change scores was observed with BF treatment for obsessive-compulsive symptoms with a mean change of 1 for BF versus 0.26 for placebo (F=6.1, p<0.02) and phobic anxiety with mean reduction of 0.98 with BF versus 0.12 for placebo (F=8.2, p<0.01, Figure 3).
   
   Who: adult men with current alcohol use disorder, abstinent under 30 days; 600 mg benfotiamine vs placebo for 6 months; high alcoholism severity subgroup
   Effect: phobic anxiety reduction 0.98 vs 0.12 (F = 8.2, p < 0.01) in high-severity subgroup; low-severity subgroup: placebo showed greater anxiety reductions
   Certainty: Subgroup analysis of a trial built for drinking outcomes; benfotiamine is a synthetic thiamine analog.
   Drug Alcohol Depend, 2015 · checked 2026-10-07 · we read the fulltext
7. ev-thax-07 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial · n = 80
   Compared to baseline and placebo supplemented values, thiamin-supplemented women experienced significantly increased appetite, energy intake, body weight and general well-being, and decreased fatigue.
   
   Who: healthy elderly Irish women from a population with marginal thiamin deficiency; thiamin 10 mg daily vs placebo
   Effect: significantly increased general well-being, appetite, energy intake, body weight; decreased fatigue (no effect sizes in abstract)
   Certainty: No anxiety scale; 1991, abstract only.
   J Gerontol, 1991 · checked 2026-10-07 · we read the abstract
8. ev-thax-08 · Randomized controlled trial(s) · randomized placebo-controlled trial · n = 66
   Vitamin B6 had a significant effect (P value < 0.025 as significant) on mood improvement compared to placebo (F (1, 27.42) = 30.25, P < 0.001, r = 0.72), but vitamin B1 had no significant effect on mood improvement compared to Placebo (F (1/35.68) = 4.76, P = 0.036, r = 0.34).
   
   Who: hospitalized patients with bipolar disorder in manic episodes on standard lithium; 100 mg B1, 40 mg B6 or placebo for 8 weeks
   Effect: B1 vs placebo on mood F = 4.76, p = 0.036 (not significant at the 0.025 threshold)
   Certainty: Mania, not anxiety.
   J Affect Disord, 2024 · checked 2026-10-07 · we read the abstract
9. ev-thax-09 · Observational data · placebo-controlled trial, randomization not stated in abstract · n = 120
   An improvement in thiamine status was associated with reports of being more clearheaded, composed and energetic.
   
   Who: young adult females, 50 mg thiamine or placebo daily for 2 months
   Effect: improved thiamine status associated with being more clearheaded, composed and energetic (no effect sizes in abstract)
   Certainty: Mood effect reported as association with status change.
   Psychopharmacology (Berl), 1997 · checked 2026-10-07 · we read the abstract
10. ev-thax-10 · Observational data · meta-analysis of observational studies · n = 13 articles, 18 studies
    The pooled RR (95% CI) of depression for the highest vs the lowest category of dietary vitamin B1, B2, B6, and B12 was 0.69 (0.55-0.87), 0.77 (0.67-0.89), 0.81 (0.71-0.93), and 0.86 (0.75-0.99), respectively.
    
    Who: observational studies of dietary B1, B2, B6, B12 intake and depression
    Effect: B1 highest vs lowest RR 0.69 (0.55-0.87)
    Certainty: Dietary B1 tracks overall diet quality; depression, not anxiety.
    Nutr Rev, 2022 · checked 2026-10-07 · we read the abstract
11. ev-thax-11 · Observational data · cross-sectional · n = —
    Before the inflection point, the effect value of the relationship was 0.68 (0.53, 0.89). After the inflection point, no significant association was found [1.10 (0.92, 1.31)].
    
    Who: American general adults, NHANES cross-sectional
    Effect: below 1.35 mg/day OR 0.68 (0.53-0.89); above OR 1.10 (0.92-1.31); overall adjusted OR 0.93 (0.82-1.07)
    Certainty: Cross-sectional, self-reported diet; suggests no benefit beyond adequate intake.
    J Affect Disord, 2024 · checked 2026-10-07 · we read the abstract
12. ev-thax-12 · Position of an expert body · agency fact sheet · n = —
    In its early stage, thiamin deficiency can cause weight loss and anorexia, confusion, short-term memory loss, and other mental signs and symptoms; muscle weakness; and cardiovascular symptoms (such as an enlarged heart) [7].
    
    Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
    Effect: early deficiency: weight loss, anorexia, confusion, short-term memory loss, mental signs; muscle weakness; cardiovascular symptoms
    Certainty: Fact sheet does not name anxiety specifically.
    NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
13. ev-thax-13 · Position of an expert body · agency fact sheet · n = —
    Because of the lack of reports of adverse effects from high thiamin intakes (50 mg/day or more) from food or supplements, the FNB did not establish ULs for thiamin [7].
    
    Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
    Effect: no UL; no adverse effects reported at 50 mg/day or more
    Certainty: Absence of reports, not proof of safety at any dose.
    NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
14. ev-thax-14 · Position of an expert body · agency fact sheet · n = —
    Up to 80% of people with chronic alcoholism develop thiamin deficiency because ethanol reduces gastrointestinal absorption of thiamin, thiamin stores in the liver, and thiamin phosphorylation [3,19].
    
    Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
    Effect: up to 80% deficient in chronic alcoholism
    Certainty: Group where low thiamine and anxiety-like symptoms most often meet.
    NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
15. ev-thax-15 · Position of an expert body · agency fact sheet · n = —
    Research has linked the use of furosemide to decreases in thiamin concentrations, possibly to deficient levels, as a result of urinary thiamin loss [49,58,59].
    
    Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
    Effect: furosemide lowers thiamin concentrations via urinary loss
    Certainty: Whether supplements prevent it is not established.
    NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
16. ev-thax-16 · Position of an expert body · agency fact sheet · n = —
    The published literature includes several cases of beriberi or Wernicke’s encephalopathy resulting from treatment with this drug, possibly because the drug might increase thiamin metabolism and block the formation of TDP, the active form of thiamin [60-63].
    
    Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
    Effect: fluorouracil may increase thiamin metabolism and block TDP formation
    Certainty: Case reports only.
    NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section