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Case Study: Caleb, an 17-Year-Old Male, with Severe Depression

While all case studies are based on actual patients, significant aspects of the case have been changed to conceal the patient’s original identity.

Initial Presentation

Caleb’s family came to me initially asking for help with their son Caleb, stating that they would prefer to avoid medications. Caleb was a 17-year-old African American youth, struggling with severe depression. Up until a year ago, Caleb had been active in school, playing both basketball and tennis. He had been getting decent grades and had an active social life. However, over the past year, Caleb had developed severe symptoms of depression, including a sense of overwhelm that had caused him to drop out of his athletic pursuits. He struggled to attend class, and due to his recent poor school performance, there were discussions about holding him back a year, delaying his high-school graduation.

And while the family wanted the best for their son, financial concerns limited his initial labs to just those covered by insurance.

Initial Relevant Labs

  • 25-hydroxy vitamin D, low at 6 ng/ml

Working Diagnosis

  • Severe depression and vitamin D deficiency

Initial Treatment

  • Vitamin D, 5000 IU daily


The incidence of severe vitamin D deficiency in the African American population is around 13-fold higher than European Americans due to darker skin pigmentation (Cui 2022). Some of the health disparities in African American populations have been attributed to the increased prevalence of this deficiency (Ames 2021).

Vitamin D deficiency has been found to increase the risk for depression (Wilczyński 2022). And at just 6 ng/ml, Caleb’s vitamin D was extremely deficient. A meta-analysis from 2023 found that vitamin D has a significant effect on treating depression, working best in those with more severe symptoms (Srifuengfung 2023). While the meta-analysis claimed that the effects were weaker in adolescents, there was only one study on children included in the analysis that did not test levels of vitamin D before supplementation.

As a treatment, vitamin D has numerous effects on mental health with vitamin D receptors found throughout the brain. When present in sufficient amounts, vitamin D influences growth factors important for the development and survival of brain cells (Moretti 2018). Vitamin D deficiency is known to increase inflammation in the brain while contributing to neurotransmitter dysregulation and dysfunction (Kasatkina 2021). Vitamin D is also involved in the synthesis and maintenance of serotonin levels (Sabir 2018, Kaviani 2020).

Follow-up Presentation

After two months of supplementation, Caleb’s vitamin D levels had started to rise into the normal range. His symptoms of depression diminished to the point where Caleb reengaged in normal activities and school work. His parents, teachers and best of all, Caleb, were all thrilled with his progress. Due to his improved school performance, talk about holding Caleb back a year had subsided and he was on track for graduating with his friends.

Follow-up Testing

  • 25-hydroxy vitamin D, 35 ng/ml

Follow-up Treatment

  • Continue 5000 iu vitamin D


Caleb’s depression was strongly rooted in a simple deficiency of vitamin D and responded dramatically to vitamin D supplementation. Research continues to show the underlying biochemical and neuroprotective effects of vitamin D on the brain, with reported benefits in a number of different mental health conditions.

Case Summary

One of the core nutrients that should be evaluated in patient’s struggling with mental illness is vitamin D. Vitamin D deficiency is common, especially in black and Hispanic populations, and often contributes to symptoms. Fortunately, treatment for vitamin D deficiency is straightforward, although tracking levels over time is advised to make sure patients maintain their levels in an appropriate therapeutic range.

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Ames BN, Grant WB, Willett WC. Does the High Prevalence of Vitamin D Deficiency in African Americans Contribute to Health Disparities?. Nutrients. 2021;13(2):499. Published 2021 Feb 3. doi:10.3390/nu13020499

Cui A, Xiao P, Ma Y, et al. Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001-2018. Front Nutr. 2022;9:965376. Published 2022 Oct 3. doi:10.3389/fnut.2022.965376

Kasatkina LA, Tarasenko AS, Krupko OO, Kuchmerovska TM, Lisakovska OO, Trikash IO. Vitamin D deficiency induces the excitation/inhibition brain imbalance and the proinflammatory shift. Int J Biochem Cell Biol. 2020;119:105665. doi:10.1016/j.biocel.2019.105665

Kaviani M, Nikooyeh B, Zand H, Yaghmaei P, Neyestani TR. Effects of vitamin D supplementation on depression and some involved neurotransmitters. J Affect Disord. 2020;269:28-35. doi:10.1016/j.jad.2020.03.029

Moretti R, Morelli ME, Caruso P. Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact. Int J Mol Sci. 2018;19(8):2245. Published 2018 Jul 31. doi:10.3390/ijms19082245

Sabir MS, Haussler MR, Mallick S, et al. Optimal vitamin D spurs serotonin: 1,25-dihydroxyvitamin D represses serotonin reuptake transport (SERT) and degradation (MAO-A) gene expression in cultured rat serotonergic neuronal cell lines. Genes Nutr. 2018;13:19. Published 2018 Jul 11. doi:10.1186/s12263-018-0605-7

Srifuengfung M, Srifuengfung S, Pummangura C, Pattanaseri K, Oon-Arom A, Srisurapanont M. Efficacy and acceptability of vitamin D supplements for depressed patients: A systematic review and meta-analysis of randomized controlled trials. Nutrition. 2023;108:111968. doi:10.1016/j.nut.2022.111968

Wilczyński KM, Chęcińska K, Kulczyk K, Janas-Kozik M. Vitamin D deficiency and depressive symptoms: meta-analysis of studies . Witamina D i objawy depresji: meta-analiza badań. Psychiatr Pol. 2022;56(6):1327-1344. doi:10.12740/PP/OnlineFirst/130992