Vitamin D deficiency has been linked to a wide range of major psychiatric illnesses and is an emerging area of interest for researchers. From my experience working with individuals with psychosis and schizophrenia in both inpatient and outpatient settings, I have often found low vitamin D levels in this patient population where the severity of symptoms were inversely correlated to serum vitamin D levels. Most recently, laboratory tests of individuals with schizophrenia, psychosis, elective mutism, and bipolar disorders revealed consistent serum vitamin D levels below 20 ng/ml. As vitamin D levels normalized, symptoms improved. While the mechanism is unclear, recent research suggests that vitamin D’s action on the regulation of inflammatory and immunological processes likely affects the manifestation of clinical symptoms and treatment response in schizophrenic patients (Chiang, Natarajan, & Fan, 2016).

The link between vitamin D deficiency and the development of schizophrenia has been researched among patients of all ages around the globe. One meta-analysis reviewed 19 studies published between 1988 and 2013 and found a strong association between vitamin D deficiency and schizophrenia. Of the 2,804 participants from these studies, over 65% of the participants with schizophrenia were vitamin D deficient. Vitamin D deficient participants were 2.16 times more likely to have schizophrenia than vitamin D sufficient participants (Valipour, Saneei, & Esmaillzadeh, 2014).

The risk of schizophrenia and vitamin D status vary with season of birth, latitude, and skin pigmentation. The UV rays required to make vitamin D are reduced in the months most associated with an increase in the birth of individuals who later develop schizophrenia. One review including a total of 437,710 individuals with schizophrenia found that most individuals were born in January and February. These newborns were thus exposed to lower levels of UV rays in their prenatal and perinatal periods. An increased rate of schizophrenia is also seen at higher latitudes, especially among immigrants. This may again be related to UV availability and subsequent vitamin D status. At higher latitudes, a dark skinned individual will also have a more pronounced reduction in vitamin D than a lighter skinned individual. The lighter skinned individual will have less melanin which allows the skin to absorb UV rays more effectively. It is estimated that individuals with darker skin at higher latitudes are more likely to develop schizophrenia than the general population (Chiang et al., 2016).

Swedish researchers reviewed medical charts at a psychiatric outpatient department to identify possible predictors of vitamin D deficiency. Over 85% of the 117 psychiatric patients had suboptimal vitamin D levels. Those with schizophrenia and autism had the lowest levels. Middle East, Mediterranean, South-East Asian or African ethnic origin were strong predictors of low vitamin D. The patients receiving vitamin D supplements to correct their deficiencies achieved considerable improvement of psychosis and depression symptoms (Humble et al., 2010).

Vitamin D concentrations were measured in 50 schizophrenia patients in Israel aged 19-65. Lower mean vitamin D concentrations were detected among patients with schizophrenia (15 ng/ml) compared to controls (20 ng/ml) after adjusting for the impact of sun exposure and supplements (Itzhaky et al., 2012). Likewise, 92% of 102 adult psychiatric inpatients in New Zealand also had suboptimal vitamin D levels and were more than twice as likely as Europeans to have severely deficient levels below <10 ng/ml (Menkes et al., 2012).

In a prospective birth cohort of 3,182 children in England, researchers measured vitamin D levels at age 9.8 years and assessed psychotic experiences at age 12.8 years. Vitamin D concentrations during childhood were associated with psychotic experiences during early adolescence. If psychotic experiences are related to the development of schizophrenia, this supports a possible protective association of higher vitamin D concentrations with schizophrenia (Tolppanen et al., 2012).

Vitamin D deficiency is associated with more severe symptoms. Cross sectional analyses were carried out on mentally ill adolescents aged 12-18 who required either inpatient or partial hospitalization. Of the 104 patients evaluated, 72% had insufficient vitamin D levels. Vitamin D status was related to mental illness severity. Those with vitamin D deficiency were 3.5 times more likely to have hallucinations, paranoia, or delusions (Gracious et al., 2012). A second study supports this finding. Vitamin D was analyzed from 20 patients with first-episode schizophrenia. Greater severity of negative symptoms (blunted affect, emotional withdrawal, poor rapport, passive-apathetic social withdrawal, abstract thinking, and stereotyped thinking) was strongly correlated with lower vitamin D status. Lower vitamin D levels were also associated with more severe overall cognitive deficits (Graham et al., 2015).

McGrath et al. (2010) investigated the relationship between neonatal vitamin D status and later risk of schizophrenia. They identified 424 cases with schizophrenia from the Danish Psychiatric Central Register and analyzed their neonatal dried blood spots. Not surprisingly they found a significant seasonal variation in vitamin D status and significantly lower levels of vitamin D in the offspring of mothers who immigrated to Denmark. They also found that those with lower neonatal concentrations of vitamin D had an increased risk of schizophrenia. The researchers estimated that if all these neonates had optimal vitamin D levels, over 40% of schizophrenia cases could have been averted.

The same group of researchers also discovered that taking vitamin D supplements during the first year of life is associated with a reduced risk of schizophrenia in males. They looked at a Finnish birth cohort and collected data about the frequency and dose of vitamin D supplementation during infancy. Males who regularly took vitamin D supplements had an 88% decreased risk of schizophrenia compared to those who never took supplements (McGrath et al., 2004).

The mechanism underlying this nutrient-illness relationship can only be speculated upon. Those with schizophrenia commonly have elevated markers of inflammation. Cells that are low in vitamin D produce high levels of inflammatory cytokines while cells with adequate vitamin D release significantly less of these cytokines. Thus there may be an anti-inflammatory mechanism (Chiang et al., 2016). Vitamin D regulates the transcription of many genes involved in pathways implicated in schizophrenia, including genes involved in synaptic plasticity, neuronal development, and protection against oxidative stress (Graham et al., 2015). Animal studies show that vitamin D deficiency in the gestational period affects dopamine metabolism and alters the dopamine system in the developing brain. Dopamine has been implicated in the pathogenesis of schizophrenia. Vitamin D deficiency during the gestational period can also affect brain structures that are associated with schizophrenia (Valipour, Saneei, & Esmaillzadeh, 2014).

While there is a lack of trials analyzing vitamin D supplements in the treatment of psychosis and schizophrenia, individuals with low levels of vitamin D within this patient population will tend to benefit from supplementation. Based on over 25 years of clinical experience, I have observed significant improvement in treatment outcomes utilizing vitamin D 5,000 to 10,000 i.u. once daily as an adjunct therapy. Serum vitamin D levels should be re-evaluated every two months until optimal levels are achieved.


  1. Chiang, M., Natarajan, R., & Xiaoduo, F. (2016). Vitamin D in schizophrenia: a clinical review. Evidence Based Mental Health, 19(1), 6-9.
  2. Cieslak, K., Feingold, J., Antonius, D., Walsh-Messinger, J., Dracxler, R., Rosedale, M., & … Malaspina, D. (2014). Low vitamin D levels predict clinical features of schizophrenia.
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  6. Humble, M. B., Gustafsson, S., & Bejerot, S. (2010). Low serum levels of 25-hydroxyvitamin D (25-OHD) among psychiatric out-patients in Sweden: Relations with season, age, ethnic origin and psychiatric diagnosis. Journal Of Steroid Biochemistry And Molecular Biology, 121(Proceedings of the 14th Vitamin D Workshop), 467-470.
  7. Itzhaky, D., Bogomolni, A., Amital, D., Arnson, Y., Amital, H., & Gorden, K. (2012). Low serum Vitamin D concentrations in patients with schizophrenia. Israel Medical Association Journal, 14(2), 88-92.
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  13. Valipour, G., Saneei, P., & Esmaillzadeh, A. (2014). Serum vitamin D levels in relation to schizophrenia: a systematic review and meta-analysis of observational studies. The Journal Of Clinical Endocrinology And Metabolism, 99(10), 3863-3872.
  14. Yüksel, R. N., Altunsoy, N., Tikir, B., Cingi Külük, M., Unal, K., Goka, S., … Goka, E. (2014). Correlation between total vitamin D levels and psychotic psychopathology in patients with schizophrenia: therapeutic implications for add-on vitamin D augmentation. Therapeutic Advances in Psychopharmacology, 4(6), 268–275.
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About the Author

James Greenblatt, MD

James M. Greenblatt, MD, dually board-certified psychiatrist, has treated patients since 1988 and is a pioneer of integrative medicine. He serves as the Chief Medical Officer at Walden Behavioral Care. He is the author of seven books, including Answers to AnorexiaFinally Focused, and upcoming book Functional & Integrative Medicine for Antidepressant Withdrawal. Dr. Greenblatt was inducted into the Orthomolecular Hall of Fame in 2017. He is also the founder of Psychiatry Redefined, an educational platform dedicated to the transformation of psychiatry, and Medical Director of TZ Health, a national virtual consultation clinic dedicated to the personalized, integrative treatment of mental illness.