Mental Health in the Sun: The Role of Vitamin D Deficiency in Mental Illness

Of the many researched integrative medicine interventions for the treatment of mental health conditions, perhaps one of the simplest is vitamin D. While controversy around its use remains, including recent guidelines that recommend against testing vitamin D levels for virtually any reason,¹ my own clinical experience combined with the latest research strongly suggest benefits for a number of mental health conditions.

Long recognized for its role in calcium metabolism and bone health, more recent research has been highlighting other important functional aspects of vitamin D. Better described as a steroid prohormone than a vitamin, vitamin D plays a prominent role as a neuroprotective agent, reducing neuroinflammation, supporting serotonin synthesis, and improving brain plasticity.² These effects are likely why the vitamin is relevant for mental health, with a growing body of research demonstrating vitamin D deficiency may have clinical implications for depression, suicide prevention, attention-deficit/hyperactivity disorder (ADHD), and anxiety treatment.

From Bone Health to Brain Health

Vitamin D was initially discovered as the cure for preventing rickets.³ Cod liver oil, rich in both vitamin A and vitamin D, was found to be effective in treating the condition. Since cod liver oil was known to be high in vitamin A, it was assumed that vitamin A was needed for the deposition of calcium in bone. However, careful experiments that removed vitamin A from cod liver oil found that it still prevented rickets, suggesting the presence of a separate nutrient, which later became known as vitamin D.

Long considered just a vitamin important for calcium absorption and bone health, research near the end of the last century started to find vitamin D receptors throughout most body tissues, including the brain.⁴ The receptor was found to influence genetic expression and affect immune function.⁵ More recently, it has been shown that vitamin D regulates neurotransmitter levels, including serotonin (Figure), through several different mechanisms.⁶ Based on this broader understanding of the effects of vitamin D, numerous studies have documented the effects of vitamin D deficiency on mental health.

Vitamin D and Depression

The most well-documented effect of vitamin D on mental health is with depression. Initially, low vitamin D was hypothesized to be a cause of seasonal affective disorder (SAD) because vitamin D levels are lower in the winter. Initial clinical trials showed benefits on mood in healthy subjects and those with SAD over the winter months.^7,8 While not all studies were positive,⁹ based on the results, research started exploring benefits in other types of patients with depression. A larger study in individuals who were overweight and had depression found significant benefits with vitamin D,¹⁰ as did a separate trial using vitamin D as an adjunctive treatment for depression when combined with standard medication.¹¹

Unfortunately, a lot of the research on vitamin D suffers from poor methodology. Many studies did not test patients' vitamin D status, or they provide the same dose of vitamin D regardless of an individual’s vitamin D levels. Other studies have used lower doses that likely minimize the clinical benefits. Even with these limitations, the latest meta-analyses have found that low vitamin D levels correlate with depression and that treatment with vitamin D provides significant improvements in depressive symptoms.^12,13

Vitamin D: A Lifeline in Suicide Prevention

The rising rates of suicide in the United States continue to be of major concern. While there are numerous calls for increasing awareness and screening, there is little discussion about direct treatment, especially of underlying biochemical risk factors. One of the more common risk factors for suicide is vitamin D deficiency.

Low vitamin D levels have been found to correlate with suicide risk. A study in 2013 found that low vitamin D was common in active military service members. They also found that the lowest levels were correlated with suicide risk.¹⁴ A study of patients with depression who attempted suicide found lower levels of vitamin D and higher levels of inflammation in the blood as compared with patients with depression who did not attempt suicide.¹⁵

A meta-analysis in 2023 found that low vitamin D was associated with suicidal behaviors.¹⁶ A retrospective study on over 300,000 veterans found that vitamin D supplementation almost halved the risk of suicide. Those who were dark-skinned or deficient in vitamin D had their suicide risk reduced by 64%.¹⁷

Vitamin D levels are easy to check and treat when found to be low. Considering the challenges around suicide prevention, adding vitamin D supplements for those who are deficient is a simple approach that could save lives.

Nourishing Young Minds: The Role of Vitamin D in ADHD

As a nutrient, vitamin D appears to be critical for normal brain development in childhood. A systematic review on vitamin D supplementation and mental health in children noted positive influences of the vitamin on numerous aspects of mental health.¹⁸ Vitamin D supplementation is recommended for mothers who are deficient during pregnancy as it appears to be protective against the development of ADHD and autism.¹⁹

A meta-analysis from 2019 found that vitamin D levels are significantly lower in children with ADHD.²⁰ That same year a separate meta-analysis looked at the effects of vitamin D supplementation on ADHD symptoms. They found that when used as an adjunctive therapy, vitamin D decreased ADHD symptoms and improved vitamin D status.²¹ It was also noted that vitamin D supplementation was devoid of serious adverse effects.

Vitamin D: Potential to Alleviate Anxiety

Vitamin D may also have benefits for reducing anxiety symptoms. A small study in patients with generalized anxiety disorder and vitamin D deficiency compared standard treatment with standard treatment plus vitamin D. For the patients treated with vitamin D, anxiety levels decreased by almost one-third compared with no significant change in the group that received standard care alone.²²

A study in women with prediabetes and low vitamin D levels also showed improvements in anxiety with vitamin D supplementation, both with and without the addition of fish oil.²³ With vitamin D alone, anxiety levels decreased 19%. When combined with fish oil, levels were reduced by 30%. In a separate study in adolescents with premenstrual syndrome and severe vitamin D deficiency, vitamin D supplementation reduced anxiety scores by 61% as compared with no appreciable change with placebo.²⁴

While these results are promising, it is worth noting that not all studies have found benefits. A study using vitamin D for depression prevention in individuals aged 60 to 80 years old did not find significant benefits for anxiety symptoms.²⁵ An earlier trial exploring the effects of vitamin D in patients with lower levels did not find significant changes in depression or anxiety symptoms.²⁶ However, in the study, depression and anxiety symptoms were quite low at baseline, as the only criterion used for selecting patients was having a low vitamin D level. Arguably, the clinical trial may have found better results if they had treated symptomatic patients with low vitamin D levels vs those without significant mental health symptoms.

My own clinical experience has highlighted the importance of testing vitamin D levels in any patient struggling with a mental health diagnosis. In patients with a deficiency, vitamin D supplementation is often helpful in reducing symptoms and improving overall wellbeing.

An Essential Yet Overlooked Laboratory Test in Psychiatry

Vitamin D deficiencies are common in patients with mental health diagnoses. The research has found benefits with vitamin D supplementation for depression, anxiety, suicide prevention, and ADHD. Research into levels of vitamin D in patients with obsessive-compulsive disorder has also found their levels to be low.^27,28 A study on subjects with posttraumatic stress disorder (PTSD) found lower levels of the vitamin.²⁹ Interestingly, the researchers also noted genetic polymorphisms of vitamin-D binding protein that correlated with lower vitamin D status in patients with PTSD. Unfortunately, guidelines around vitamin D testing and supplementation overlook most data suggesting benefits beyond bone health.

I have found vitamin D deficiency to be a key component that is often ignored by psychiatry. The simplest approach to identify patients who need supplementation is through testing. In patients with a severe deficiency, higher doses may be necessary to achieve optimum levels. Testing is also critical to monitor the vitamin D levels of some patients who have poor absorption of vitamin D supplements.

The core principle of integrative medicine is biochemical individuality: recognizing that all patients are different and have different genetic variability and environmental stressors. Vitamin D testing and treatment can be 1 simple step toward incorporating personalized medicine into psychiatry.

While vitamin D should not be seen as a silver-bullet cure-all for mental health problems, it is a fundamental nutrient that is vital for the normal function of brain neurochemistry. It is also commonly deficient. Supporting vitamin D is foundational for developing a personalized approach to mental health care and for supporting the efficacy of other treatments. Considering how many patients with mental health conditions struggle with residual symptoms even with standard treatment, simple interventions, like vitamin D, could have a profound impact on the health of our patients.

Dr Greenblatt is the chief medical officer of Psychiatry Redefined, an online educational platform for integrative and functional psychiatry.

References

1. Shah VP, Nayfeh T, Alsawaf Y, et al. A systematic review supporting the Endocrine Society Clinical Practice Guidelines on vitamin D. J Clin Endocrinol Metab. 2024;109(8):1961-1974.

2. Menéndez SG, Manucha W. Vitamin D as a modulator of neuroinflammation: implications for brain health. Curr Pharm Des. 2024;30(5):323-332.

3. McCollum EV, Simmonds N, Becker JE, Shipley PG. Studies on experimental rickets: XXI. an experimental demonstration of the existence of a vitamin which promotes calcium deposition. J Biol Chem. 1922;53(2):293-312.

4. Haussler MR, Whitfield GK, Haussler CA, et al. The nuclear vitamin D receptor: biological and molecular regulatory properties revealed. J Bone Miner Res. 1998;13(3):325-349.

5. DeLuca HF, Zierold C. Mechanisms and functions of vitamin D. Nutr Rev. 1998;56(2 Pt 2):S4-10; discussion S 54-75.

6. Cui X, Gooch H, Petty A, et al. Vitamin D and the brain: genomic and non-genomic actions. Mol Cell Endocrinol. 2017;453:131-143.

7. Lansdowne AT, Provost SC. Vitamin D3 enhances mood in healthy subjects during winter. Psychopharmacology (Berl). 1998;135(4):319-323.

8. Gloth FM, Alam W, Hollis B. Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder. J Nutr Health Aging. 1999;3(1):5-7.

9. Dumville JC, Miles JNV, Porthouse J, et al. Can vitamin D supplementation prevent winter-time blues? A randomised trial among older women. J Nutr Health Aging. 2006;10(2):151-153.

10. Jorde R, Sneve M, Figenschau Y, et al. Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial. J Intern Med. 2008;264(6):599-609.

11. Khoraminya N, Tehrani-Doost M, Jazayeri S, et al. Therapeutic effects of vitamin D as adjunctive therapy to fluoxetine in patients with major depressive disorder. Aust N Z J Psychiatry. 2013;47(3):271-275.

12. Wilczyński KM, Chęcińska K, Kulczyk K, Janas-Kozik M. Vitamin D deficiency and depressive symptoms: meta-analysis of studies. Psychiatr Pol. 2022;56(6):1327-1344.

13. Srifuengfung M, Srifuengfung S, Pummangura C, et al. Efficacy and acceptability of vitamin D supplements for depressed patients: a systematic review and meta-analysis of randomized controlled trials. Nutrition. 2023;108:111968.

14. Umhau JC, George DT, Heaney RP, et al. Low vitamin D status and suicide: a case-control study of active duty military service members. PLoS One. 2013;8(1):e51543.

15. Grudet C, Malm J, Westrin A, Brundin L. Suicidal patients are deficient in vitamin D, associated with a pro-inflammatory status in the blood. Psychoneuroendocrinology. 2014;50:210-219.

16. Mohammadi Y, Ansari N, Daneshi Maskooni M, Amiri MR. Association of vitamin D with suicide behaviors: a systematic review and meta-analysis. Iran J Psychiatry. 2023;18(4):484-492.

17. Lavigne JE, Gibbons JB. The association between vitamin D serum levels, supplementation, and suicide attempts and intentional self-harm. PLoS One. 2023;18(2):e0279166.

18. Głąbska D, Kołota A, Lachowicz K, et al. The influence of vitamin D intake and status on mental health in children: a systematic review. Nutrients. 2021;13(3):952.

19. Chien MC, Huang CY, Wang JH, et al. Effects of vitamin D in pregnancy on maternal and offspring health-related outcomes: an umbrella review of systematic review and meta-analyses. Nutr Diabetes. 2024;14(1):35.

20. Kotsi E, Kotsi E, Perrea DN. Vitamin D levels in children and adolescents with attention-deficit hyperactivity disorder (ADHD): a meta-analysis. Atten Defic Hyperact Disord. 2019;11(3):221-232.

21. Gan J, Galer P, Ma D, et al. The effect of vitamin D supplementation on attention-deficit/hyperactivity disorder: a systematic review and meta-analysis of randomized controlled trials. J Child Adolesc Psychopharmacol. 2019;29(9):670-687.

22. Eid A, Khoja S, AlGhamdi S, et al. Vitamin D supplementation ameliorates severity of generalized anxiety disorder (GAD). Metab Brain Dis. 2019;34(6):1781-1786.

23. Rajabi‐Naeeni M, Dolatian M, Qorbani M, Vaezi AA. Effect of omega‐3 and vitamin D co‐supplementation on psychological distress in reproductive‐aged women with pre‐diabetes and hypovitaminosis D: a randomized controlled trial. Brain Behav. 2021;11(11):e2342.

24. Tartagni M, Cicinelli MV, Tartagni MV, et al. Vitamin D supplementation for premenstrual syndrome-related mood disorders in adolescents with severe hypovitaminosis D. J Pediatr Adolesc Gynecol. 2016;29(4):357-361.

25. de Koning EJ, Lips P, Penninx BWJH, et al. Vitamin D supplementation for the prevention of depression and poor physical function in older persons: the D-Vitaal study, a randomized clinical trial. Am J Clin Nutr. 2019;110(5):1119-1130.

26. Kjærgaard M, Waterloo K, Wang C, et al. Effect of vitamin D supplement on depression scores in people with low levels of serum 25-hydroxyvitamin D: nested case-control study and randomised clinical trial. Br J Psychiatry. 2012;201(5):360-368.

27. Soyak HM, Karakükcü Ç. Investıgation of vitamin D levels in obsessive-compulsive disorder. Indian J Psychiatry. 2022;64(4):349-353.

28. Marazziti D, Barberi FM, Fontenelle L, et al. Decreased vitamin D levels in obsessive-compulsive disorder patients. CNS Spectr. 2023;28(5):606-613.

29. Terock J, Hannemann A, Van der Auwera S, et al. Posttraumatic stress disorder is associated with reduced vitamin D levels and functional polymorphisms of the vitamin D binding-protein in a population-based sample. Prog Neuropsychopharmacol Biol Psychiatry. 2020;96:109760.