Vitamin B9
Folate and folic acid, a B vitamin
A B vitamin also called folate in food and folic acid in supplements, found in leafy greens, peas and chickpeas. Supplements also use L-methylfolate (5-MTHF) and folinic acid. This page covers only studies in people that measured thinking, memory, mood, stress, sleep, energy, tiredness or quality of life, not all research on vitamin B9. In those, it is studied mostly for thinking and memory, and for mood alongside antidepressants. Here is every one we could find, sorted from each study's summary.
- Found in: leafy greens, peas and chickpeas
- Doses range from 150 to 15,000 µg a day
- Mostly taken daily for weeks or months
From every paper to the studies that matter
Our search looked only at vitamin B9 papers on thinking, memory, mood, stress, sleep, energy, tiredness and quality of life, not at all research on the vitamin. Many of those only measure folate in the blood or diet, or look at genes, and are left out. A smaller share gives vitamin B9 to people, and that is what this page is about.
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6,071 papers on vitamin B9 and thinking, mood, sleep or energy.Every record in PubMed, all years
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553 are about people.The rest: 922 lab and animal studies, 1,197 reviews, 3,399 on chemistry, farming and more
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89 give vitamin B9 on its own.152 more give it with iron, other vitamins or other nutrients, or in a blend
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50 are randomised against a placebo.Randomised controlled trials In a randomised controlled trial, people are put into groups by chance, one taking the treatment and one a placebo or other comparison. Chance spreads differences such as age and health evenly, so a difference between the groups is more likely to be down to the treatment., the strongest kind of study
Bar lengths use a square-root scale so the small numbers stay visible.
How much research there is
- 89 studies giving vitamin B9 to people, on thinking, mood, sleep and energy
- 50 of them randomised against a placebo A placebo-controlled trial compares a real treatment with a dummy that looks the same, the placebo. People often feel better when they expect to, so comparing against a placebo shows how much of the change comes from the treatment itself.
- 11,527 people taking part, where studies say
- 257 systematic reviews A systematic review searches for every study on a question in a set, written-down way, judges the quality of each and sums up what they show together. Many include a meta-analysis. The Atlas lists these as pooled reviews. pooling the trials
Studies in people, by year published
Vitamin B9 on its own, always by mouth.
What the studies looked at
Each study can measure several things. Choose a topic to see its studies in the list below.
Studies in people with a diagnosed condition are counted here and listed with their population. We describe what they measured, not what they might treat. Most studies also report safety; see below.
What was tested, and how much
Doses are shown in micrograms (µg) a day. They range widely, from about 150 µg to 15,000 µg (15 mg). Many studies gave 15,000 µg of L-methylfolate, a prescription-strength dose used alongside antidepressants, so it is not a typical supplement dose. Others gave 400 to 800 µg of folic acid, and some gave 5,000 µg or more. A few dots far to the right are very large doses. Folic acid, L-methylfolate and folinic acid are different forms, so doses may not compare exactly. Most studies gave the vitamin every day for weeks or months.
Daily amount, one dot per study
Studies per extract
Named extracts are the maker's brand. "Not named" means the study didn't say.
All studies in people
Filter the list, then open a study on PubMed. Each row comes from the study's published summary. Many follow people with a health condition, such as low mood treated with antidepressants or memory problems in later life.
| Study | Who took part | People | Extract and daily dose | Length |
|---|---|---|---|---|
| Liu 2026RCT, placebo | Cerebral small vessel disease with cognitive impairment | 220 | Folic acid, 800 µg | 26 weeks |
| Mohammadizadeh 2026RCT, placebo | Postpartum mothers | 60 | Folic acid, 500 µg | 9 weeks |
| Yoshida 2026RCT, active or other control | Rheumatic disease patients on methotrexate | 44 | Folic acid, 1,430 µg | 12 weeks |
| Ghiasi 2025RCT, placebo | Children of high-risk pregnant women, followed to age 4-9 | 664 | Folic acid, 4,000 µg | – |
| Jing 2025RCT, active or other control | Alzheimer's patients on donepezil | 114 | Folic acid | 13 weeks |
| Galal 2025RCT, active or other control | Adults with CKD stages 3-5 | 80 | Folic acid | 26 weeks |
| Siddique 2025Non-randomised controlled | Adults with depressive disorder on antidepressants | 44 | L-methylfolate, 800 µg | 4 weeks |
| Liu 2024RCT, placebo | Adults with mild cognitive impairment and low vitamin D | 402 | Folic acid | 24 weeks |
| Li 2024RCT, placebo | Older adults with mild cognitive impairment | 280 | Folic acid, 800 µg | 52 weeks |
| Bai 2024RCT, placebo | Older adults with mild cognitive impairment, follow-up after stopping | 160 | Folic acid | 26 weeks |
| Carmon 2024Single-arm or open-label | Adults with sleep complaints and reduced MTHFR activity | 10 | L-methylfolate, 5,000 µg | 8 weeks |
| Hilman 2024RCT, placebo | Children of mothers given folic acid in pregnancy, age 11 | – | Folic acid | – |
| Bopp 2022Non-randomised controlled | Youths with unipolar depression | 412 | L-methylfolate | – |
| Ondičová 2022RCT, placebo | Pregnant women and their children | – | Folic acid, 400 µg | – |
| van Soest 2021RCT, placebo | Older adults with raised homocysteine | 791 | Folic acid, 800 µg | 156 weeks |
| Li 2021RCT, placebo | Older adults with mild cognitive impairment | 240 | Folic acid, 800 µg | 26 weeks |
| Carter 2021RCT, placebo | Antidepressant-treated depressed patients with low B12 | 177 | Folic acid, 5,000 µg | 12 weeks |
| Caffrey 2021RCT, placebo | Children of mothers given folic acid in pregnancy | 119 | Folic acid, 400 µg | – |
| Saxena 2021Non-randomised controlled | Elderly inpatients with treatment-resistant depression | 115 | Folinic acid (leucovorin) | – |
| Kvestad 2020RCT, placebo | Children in North India, follow-up at 6-9 years | 1,000 | Folic acid, 150 µg | 26 weeks |
| Campoy 2020RCT, placebo | Children of mothers supplemented in pregnancy | 143 | 5-MTHF | – |
| Zhilyaeva 2020Non-randomised controlled | Schizophrenia patients, MTHFR T allele carriers | 75 | Folic acid; L-methylfolate (Metafolin) | 4 weeks |
| Hama 2020Single-arm or open-label | Older adults with folate deficiency and cognitive impairment | 45 | Folic acid, 5,000 µg | 6 weeks |
| Ma 2019RCT, active or other control | Older adults with mild cognitive impairment | 240 | Folic acid | 26 weeks |
| Rainka 2019Observational | Children and adolescents at psychiatry clinic | 190 | L-methylfolate, 15,000 µg | – |
| Ma 2019RCT, active or other control | Adults with mild cognitive impairment | 180 | Folic acid, 400 µg | 104 weeks |
| Catena 2019RCT, placebo | Children aged 10 of supplemented mothers | 74 | 5-MTHF | – |
| McNulty 2019RCT, placebo | Children of mothers given folic acid in pregnancy | 70 | Folic acid, 400 µg | 26 weeks |
| Surman 2019RCT, placebo | Adults with ADHD on methylphenidate | 44 | L-methylfolate, 15,000 µg | 12 weeks |
| Dartois 2019Single-arm or open-label | Adolescents with treatment-resistant depression | 10 | L-methylfolate | – |
| Simon 2018RCT, placebo | Adults with bipolar depression | 201 | Folic acid | 52 weeks |
| Riahi 2018RCT, placebo | Children with ADHD taking methylphenidate | 70 | Folic acid, 5,000 µg | 8 weeks |
| Roffman 2018RCT, placebo | Outpatients with schizophrenia on antipsychotics | 55 | L-methylfolate, 15,000 µg | 12 weeks |
| Nierenberg 2017Single-arm or open-label | Adults with bipolar I depression | 10 | L-methylfolate, 15,000 µg | 6 weeks |
| Tunbridge 2017RCT, placebo | Adults with bipolar depression on quetiapine | – | Folic acid | 12 weeks |
| Christian 2016RCT, placebo | Pregnant Nepalese women, folic acid arm vs vitamin A control | 737 | Folic acid | – |
| Geddes 2016RCT, placebo | Adults with bipolar depression on quetiapine | 202 | Folic acid | 12 weeks |
| Ma 2016RCT, active or other control | Older adults with mild cognitive impairment | 180 | Folic acid, 400 µg | 26 weeks |
| Ma 2016RCT, active or other control | Elderly with mild cognitive impairment | 152 | Folic acid, 400 µg | 52 weeks |
| Catena 2016RCT, placebo | Children aged 8.5 whose mothers took prenatal 5-MTHF | 136 | 5-MTHF | – |
| Chen 2016RCT, active or other control | Alzheimer's patients taking donepezil | 121 | Folic acid, 1,250 µg | 26 weeks |
| Zajecka 2016Single-arm or open-label | Adults with depression on SSRI, inadequate response | 68 | L-methylfolate calcium, 15,000 µg | 52 weeks |
| Sun 2016Non-randomised controlled | Children with autism in structured teaching | 66 | Folic acid, 800 µg | 13 weeks |
| Shelton 2015RCT, placebo | Adults with depression and inadequate SSRI response | – | L-methylfolate calcium, 15,000 µg | 9 weeks |
| Wade 2014Observational | Adults with depression on SSRI/SNRI augmentation | 5,404 | L-methylfolate, 7,500 µg | – |
| Bedson 2014RCT, placebo | Adults with depression taking antidepressants | 475 | Folic acid, 5,000 µg | 12 weeks |
| Van Der Woude 2014RCT, active or other control | Postpartum women with anemia | 112 | Folic acid, 1,000 µg | 4 weeks |
| Sharpley 2014RCT, placebo | Young people at familial risk of mood disorder | 112 | Folic acid, 2,500 µg | 156 weeks |
| Papakostas 2014RCT, placebo | Adults with SSRI-resistant major depression | 75 | L-methylfolate, 15,000 µg | 9 weeks |
| Shelton 2013Single-arm or open-label | Adults treated for major depression | 554 | L-methylfolate (Deplin) | 14 weeks |
| Tabei 2013Non-randomised controlled | Children with beta-thalassemia minor | 73 | Folic acid, 1,000 µg | 12 weeks |
| Ghanizadeh 2013RCT, placebo | Children with ADHD on methylphenidate | 49 | Folic acid, 5,000 µg | 8 weeks |
| Venkatasubramanian 2013RCT, active or other control | Women with depression on fluoxetine | 42 | Folic acid, 5,000 µg | 6 weeks |
| Loria-Kohen 2013RCT, placebo | Patients with eating disorders and low folate intake | 24 | Folic acid (ACFOL), 10,000 µg | 26 weeks |
| Frye 2013Non-randomised controlled | Children with autism and folate receptor antibodies | – | Leucovorin calcium | 17 weeks |
| Papakostas 2012RCT, placebo | Adults with SSRI-resistant major depression | 223 | L-methylfolate, 15,000 µg | 9 weeks |
| Ginsberg 2011Observational | Adults with major depressive episode | 242 | L-methylfolate | – |
| Blehaut 2010RCT, placebo | Children with Down syndrome aged 3-30 months | 113 | Folinic acid (leucovorin) | 52 weeks |
| Connelly 2008RCT, placebo | Alzheimer's disease outpatients on cholinesterase inhibitors | 57 | Folic acid, 1,000 µg | 26 weeks |
| Resler 2008RCT, placebo | Major depression patients on fluoxetine | 27 | Folic acid, 10,000 µg | 6 weeks |
| Sander 2008RCT, placebo | Adults aged 50-70 with raised homocysteine | – | Folic acid | 156 weeks |
| Durga 2007RCT, placebo | Adults 50-70 with raised homocysteine | 818 | Folic acid, 800 µg | 156 weeks |
| Lundell 2006Single-arm or open-label | Chronic fatigue syndrome patients | 58 | Folinic acid | – |
| Pathansali 2006RCT, placebo | Healthy elderly with normal folate | 24 | Folic acid, 5,000 µg | 4 weeks |
| Williams 2005RCT, placebo | Healthy folate-replete males | 23 | Folic acid, 200 µg | 12 weeks |
| Hernández 2005RCT, placebo | Epilepsy patients on phenytoin or carbamazepine | 18 | Folic acid, 5,000 µg | 26 weeks |
| Sommer 2003Non-randomised controlled | Patients with dementia, low-normal folate | 11 | Folic acid, 10,000 µg | – |
| Bryan 2002RCT, placebo | Healthy women, younger to older | 211 | Folic acid, 750 µg | 5 weeks |
| Alpert 2002Single-arm or open-label | Adults with SSRI-refractory depression | 22 | Folinic acid (leucovorin) | 8 weeks |
| Yukawa 2001Single-arm or open-label | Neurological patients with low serum folate | 36 | Folic acid, 15,000 µg | – |
| Coppen 2000RCT, placebo | Adults with major depression on fluoxetine | 127 | Folic acid, 500 µg | 10 weeks |
| Fioravanti 1998RCT, placebo | Elderly with cognitive decline and low folate | 30 | Folic acid | 9 weeks |
| Passeri 1993RCT, active or other control | Elderly with dementia and depression | 96 | 5-MTHF, 50,000 µg | 8 weeks |
| Guaraldi 1993Single-arm or open-label | Elderly adults with depression | 20 | L-methylfolate, 50,000 µg | 6 weeks |
| Strom 1992Crossover, placebo | Males with fragile X syndrome | 21 | Folinic acid, 15,000 µg | 13 weeks |
| Procter 1991RCT, placebo | Psychiatric inpatients with low folate | 41 | Methylfolate, 15,000 µg | 26 weeks |
| Godfrey 1990RCT, placebo | Psychiatric inpatients with low folate | 41 | Methylfolate, 15,000 µg | 26 weeks |
| Lejeune 1989Single-arm or open-label | Trisomy 21 patients with psychosis or regression | 39 | Folinic acid | – |
| Madison 1986Crossover, placebo | Males with fragile X syndrome | 3 | Folic acid, 10,000 µg | – |
| Rosenblatt 1985Crossover, placebo | Identical twin boys with fragile X | 2 | Folic acid, 10,000 µg | 13 weeks |
| Botez 1984Single-arm or open-label | Patients with folate deficiency and brain damage | 49 | Folic acid, 10,000 µg | 39 weeks |
| Brown 1984Crossover, placebo | Brothers with fragile X | 2 | Folic acid | – |
| Botez 1982Single-arm or open-label | Folate-deficient neuropsychiatric patients | – | Folic acid | – |
| Gibberd 1981RCT, placebo | Epilepsy outpatients on phenytoin | – | Folic acid | 52 weeks |
| Botez 1977Single-arm or open-label | Patients with folate-responsive neuropsychiatric disorders | 16 | Folic acid | 39 weeks |
| Ueda 1977Single-arm or open-label | Epileptic patients with psychiatric symptoms | 15 | Folic acid | – |
| Botez 1976Single-arm or open-label | Women with folate deficiency, neuropsychiatric signs | 6 | Folic acid | – |
| Shaw 1971Other | Senile dementia patients | – | Folate | – |
| Grant 1970RCT, placebo | Folate-deficient epilepsy patients | 51 | Folic acid, 15,000 µg | 26 weeks |
What's known about safety
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In trials
The two meta-analyses of L-methylfolate or folic acid added to antidepressants that we opened reported on symptom scores and response, and their summaries did not report side effects. For folic acid medicines, the NHS lists bloating, wind, nausea and loss of appetite as possible side effects of tablets, and diarrhoea, vomiting and an itchy rash for the liquid.
Maruf 2021, meta-analysis of L-methylfolate in depression; Altaf 2021, meta-analysis of folate added to SSRIs or SNRIs (PubMed summaries); NHS folic acid medicine page, Oct 2026
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In the UK
Folic acid, calcium-L-methylfolate and the glucosamine salt of L-methylfolate are on the permitted list for food supplements. The NHS says taking 1 mg or less a day of folic acid supplements is unlikely to cause harm, and advises 400 µg a day for anyone pregnant, trying for a baby or who could get pregnant, until 12 weeks of pregnancy. Some women are advised a higher 5 mg dose by a doctor.
Directive 2002/46/EC Annex II as retained in UK law (legislation.gov.uk); NHS vitamins and minerals pages on B vitamins and folic acid, Oct 2026
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Check first
The NHS says doses of folic acid above 1 mg can mask the symptoms of vitamin B12 deficiency, which can eventually damage the nervous system if it isn't spotted and treated, and this is a particular concern for older people. It lists epilepsy medicines such as phenytoin, phenobarbital and primidone, some antibiotics, sulfasalazine, lithium and aspirin among medicines that may not mix well with folic acid, and says folic acid may not suit people with B12 deficiency anaemia or a coronary stent. Speak to a pharmacist or doctor first if any of these apply to you.
NHS vitamins and minerals page on B vitamins and folic acid; NHS folic acid medicine page, Oct 2026
Where these studies come from
We list every published study in people that gave vitamin B9 and measured thinking, memory, attention, mood, stress, anxiety, sleep, energy, tiredness or quality of life, as folic acid, folate, L-methylfolate (5-MTHF) or folinic acid given as a vitamin. Vitamin B9 added to a medicine or usual care and compared with that care alone counts as on its own; folic acid given with iron, other vitamins or other nutrients counts as a blend. Studies that only measured folate (blood levels, diet surveys, genes such as MTHFR) are left out, as are studies where only the control group got it, folinic acid (leucovorin) given as rescue with methotrexate or chemotherapy, and antifolate drugs. This page is not a review of everything known about the vitamin. This first version is built from each study's summary; full-paper checks come next.
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We search
PubMed, the world's main library of medical research, for every paper on L-theanine.
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We keep studies in people
Lab and animal work is counted but left out of the list, because it doesn't tell you what happens in people.
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We note the basics
Who took part, how many, how much and for how long, from each study's published summary. A second check corrects what the first read gets wrong.
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We read them in full
Results appear once we've read the whole paper and checked every number. The date at the top shows when this entry was last updated.
Download the study list
Every study in people as a spreadsheet, 89 rows, free to reuse with a link back.
Versions
Each update to the data gets a new version number, so you can tell what changed and when.
See every version
1.0 · 24 Oct 2026. First release. Every published study giving vitamin B9 to people that measured thinking, memory, mood, stress, sleep, energy or quality of life is listed from its summary. None is read in full yet.
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