Low iron levels can cause fatigue and other symptoms that develop gradually as iron stores worsen. The article lists weakness, fatigue, pale skin, shortness of breath, dizziness, headaches, cold hands and feet, and restless legs among common symptoms of iron-deficiency anemia.

Extensive empirical evidence indicates that deficiencies in vitamin D, B vitamins, and other micronutrients are linked to an increased incidence of depression, especially among women and overweight older adults. In the neuropsychiatric domain, vitamin D deficiency has been robustly linked to an elevated risk of depression in older adults. Clinical evidence indicates that low levels of vitamin B1, B5, B6, and B9 are prevalent among late-life depression patients, with their deficiencies significantly correlated with the severity of depression and the rate of cognitive decline.

Deficiency of this particular vitamin can lead to fatigue, weakness, constipation, balance issues, mental fogginess, peripheral tingling, depression, and cognitive issues. Deficiency of Vitamin B12 can result in hematological changes, neurological and psychiatric problems, which can manifest as irritability, changes in personality, depression, and memory loss. Based on the reviewed studies, it was found that although there is no concrete evidence showing positive effects of Vitamin B12 on depression or depressive symptoms, the lower levels of Vitamin B12 in the body are associated with a higher risk of developing depression.

This review summarizes that many studies report vitamin D deficiency is associated with symptoms of depression and anxiety. It cites a 4‑year cohort study in which individuals with vitamin D deficiency were 75% more likely to develop depression than those with adequate levels, indicating that low vitamin D status is linked to depressive symptoms such as low mood and loss of interest.[29]

Megaloblastic anemia is the common and serious illness associated with B12 deficiency, but it is believed that a mild decrease in the B12 level is associated with neurologic and psychiatric problems such as ataxia or mood disturbances. Depression, dementia, and mental impairment are often associated with vitamin B12 and folate deficiency, especially in the elderly. Psychiatric manifestations can occur in the presence of low serum B12 levels but in the absence of the other well-recognized neurologic and hematologic abnormalities of pernicious anemia. Such symptoms may precede hematologic symptoms by months or years and may present as the only symptoms related to deficiency.

The patient information page says iron-deficiency anemia symptoms may include unexplained fatigue or lack of energy, shortness of breath, generalized weakness, headache, lightheadedness or dizziness, and poor sleep.

Hyperhomocysteinemia, vitamin B12 deficiency, and to a lesser extent, folate deficiency were all related to depressive disorders. For folate deficiency and hyperhomocysteinemia, the association with depressive disorders was substantially reduced after adjustment for functional disability and cardiovascular disease, but for vitamin B12 this appeared independent. Vitamin B12 may be causally related to depression, whereas the relation with folate is due to physical comorbidity.

In community-dwelling older women, metabolically significant vitamin B12 deficiency is associated with a twofold risk of severe depression. We found that community-dwelling older physically disabled women with metabolically significant vitamin B12 deficiency had a risk of depression that was more than twice as high as that of women without vitamin B12 deficiency. These findings suggest that vitamin B12 deficiency may contribute to the development of severe depressive symptoms in this population.

Lower vitamin D levels were found in people with depression compared with controls (SMD = 0.60, 95% CI 0.23–0.97). The cohort studies showed a significantly increased hazard ratio of depression for the lowest vs highest vitamin D categories (HR = 2.21, 95% CI 1.40–3.49). The authors conclude: "Our analyses are consistent with the hypothesis that low vitamin D concentration is associated with depression" and highlight the need for randomized trials to assess causality.

This meta-analysis of 20 randomized controlled trials found that vitamin D supplementation significantly reduced depressive symptom scores compared to controls (standardized mean difference [SMD] = –0.36; 95% CI, –0.52 to –0.20; P < 0.00001). The authors conclude that vitamin D supplementation is associated with a moderate but statistically significant improvement in depressive symptoms and support its potential role as an adjunctive treatment for depression, particularly in individuals with baseline deficiency (<20 ng/mL).

Low iron levels can cause fatigue and affect mood; the page says iron deficiency can make people feel tired, have trouble thinking, and affect their mood, and lists changes in mood among symptoms of low iron.

Deficiencies in nutrients such as protein, B vitamins, vitamin D, magnesium, zinc, selenium, iron, calcium, and omega-3 fatty acids have a significant impact on brain and nervous system function, which can affect the appearance of depressive symptoms. Both excess and deficiency of copper and iron may affect the risk of depression.

This critical appraisal states that "Overall findings were that there is a relationship between vitamin D and depression, though the directionality of this association remains unclear." It notes that serum vitamin D levels inversely correlate with clinical depression, and evidence from supplementation trials suggests a more robust therapeutic effect in subjects with major depression and concurrent vitamin D deficiency, but the authors caution the evidence is not strong enough to recommend universal supplementation.

This systematic review identified one case–control study, ten cross-sectional studies and three cohort studies examining vitamin D deficiency and depression. Meta-analysis of cross-sectional studies showed an increased but borderline non‑significant odds of depression for the lowest vs highest vitamin D categories (OR = 1.31, 95% CI 1.00–1.71, P = 0.05). The authors state that the observational studies provide some evidence for a relationship between vitamin D deficiency and depression but note that overall evidence quality is low and randomized controlled trials are urgently needed to determine whether vitamin D can prevent and treat depression.

Identifying and managing deficiencies in essential fatty acids, magnesium, zinc, B vitamins (folate, B12), and vitamin D is critical in individuals with depression. Healthy dietary patterns include adequate amounts of n-3 essential fatty acids, vitamin B12, magnesium, and zinc required for normal physiological functioning, and because suboptimal intake of these nutrients has been associated with increased risk of depression, deficiencies should be treated.

In this large randomized clinical trial of 18,353 adults aged 50 years or older without depression at baseline, daily vitamin D3 supplementation compared with placebo "did not result in statistically significant differences in the incidence and recurrence of depression or clinically relevant depressive symptoms" (hazard ratio, 0.97) or in change in mood scores over 5 years. These findings suggest that in generally healthy adults, long‑term vitamin D3 did not prevent development of depressive symptoms, despite observational links between low vitamin D and depression.

Fatigue is described as the main symptom of iron deficiency, and patients may experience deterioration of motivation to perform daily tasks, feelings of physical tiredness, or problems with concentration before they become anemic.

Several micronutrient deficiencies adversely affect the brain and hence could aggravate mental disorders like schizophrenia, depression and anorexia nervosa. It is plausible that proper attention to diet and, when indicated, appropriate supplementation with vitamin C, folic acid, niacin, thiamine, iron, zinc, omega-3 fatty acids, vitamin D and vitamin E could lower the dosage requirement for antipsychotic drugs and reduce their adverse side effects and toxicity.

Low folate and B12 concentrations have been correlated with depressive disorders, while evidence has suggested that both of these vitamins may enhance the effectiveness of antidepressants. In this population representative study, we observed that those with deficient-low B12 status had a 51% increased likelihood of developing depressive symptoms over 4 years. In conclusion, we observed that low B12 status was associated with a significantly increased risk of depressive symptoms over 4-year period in a large population representative study of older adults. No associations were observed for folate.

This systematic review and meta-analysis of randomized controlled trials reports that vitamin D supplementation produced a statistically significant improvement in mean depression scores when doses ≥4000 IU were administered (SMD: 0.116 [95% CI: 0.015–0.218]). The authors conclude that vitamin D supplementation at higher doses may be effective in reducing depressive symptoms, although effect sizes are small and study heterogeneity exists.

Using a nationally representative US sample, this preprint concludes: "Vitamin D deficiency is modestly but significantly associated with depressive symptoms, particularly little interest and low energy." The authors found that vitamin D deficiency was modestly associated with increased odds of specific depressive symptoms such as anhedonia and fatigue, supporting that low vitamin D status can be linked to mood-related symptoms that overlap with depression.

Pyridoxine (B6) deficiency may lead to irritability, depression, and cognitive impairment, as well as epilepsy and cerebrovascular diseases. Symptoms related to folate deficiency include fatigue, apathy, insomnia, impaired concentration, and irritability. Deficiencies in complex B vitamins, particularly vitamins B9 (folate) and B12 (cobalamin), have significant neuropsychiatric manifestations that can profoundly impact mental and neurological health, including depression and cognitive decline.

Among these, decreased micronutrient concentrations were associated with increased depressive symptoms for iron, calcium, manganese, potassium, vitamin D, vitamin E, zinc, vitamin B-6, folate, vitamin B-12, and vitamin C. In conclusion, despite several cross-sectional studies examining the association of micronutrients such as vitamin D, iron, and zinc with depression among children and adolescents, there was an overwhelming lack of randomized controlled trials for all micronutrients.

In particular, vitamins B1, B3, B6, B9 and B12 are essential for neuronal function and deficiencies have been linked to depression. Deficiency of these vitamins may contribute to the onset of depressive symptoms by altering neurotransmitter synthesis and brain energy metabolism. The review concludes that adequate intake and status of B vitamins may be important in preventing or alleviating depressive disorders.

This case series notes that a prior systematic review and meta-analysis of seven randomized controlled trials "has noted the unequivocal effect of vitamin D supplementation as an antidepressant." Another systematic review and meta-analysis cited found that low vitamin D concentration is associated with depression, but emphasized the need for robust randomized controlled trials to confirm a causal relation between vitamin D deficiency and depression. The article describes clinical cases where vitamin D repletion was associated with improvement in depressive symptoms.

There is a possible relationship between vitamin B12 deficiency and depression, with evidence that supplementation may alleviate symptoms in adults treated with selective serotonin reuptake inhibitors. The current findings suggest that vitamin B12 deficiency could contribute to the onset or exacerbation of depressive symptoms, possibly through homocysteine accumulation and alterations in neurotransmitter synthesis. Although this association has been found, a direct causal relationship has yet to be established, which requires more rigorous research.

This narrative review states: "Our literature review found substantial evidence for a significant relationship between depression and vitamin D deficiency" but also highlights that more studies are needed to establish the direction of causality and optimal prevention/treatment strategies. It cites the Third National Health and Nutrition Examination Survey, which found that people with serum vitamin D ≤50 nmol/L were at significantly higher risk of showing depression than individuals with levels ≥75 nmol/L, indicating that low vitamin D is associated with depressive symptoms.

Deficiencies in vitamin B12 and folate are frequently linked with mood disorders, particularly those of a depressive nature. The neuropsychiatric manifestations of these two deficiencies significantly overlap, although it has been suggested that vitamin B12 deficiency may have a more pronounced effect on peripheral nerves and the spinal cord, while folate deficiency may more significantly impact brain function. This brief report describes a mood disorder with mixed features due to combined vitamin B12 and folate deficiency, illustrating how such deficiencies can present with prominent depressive symptoms.

The article says iron levels can produce fatigue, brain fog, sleeplessness, and other debilitating symptoms, and quotes a clinician saying iron deficiency is often underrecognized and underdiagnosed because its symptoms overlap with other conditions.

Vitamin D deficiency is linked to depression, anxiety, and cognitive decline. Nutritional interventions, including vitamin D, B12, zinc, and probiotics, show promise as adjunctive therapies or preventive strategies for mental disorders. Low serum concentrations of vitamin B12 are associated with the development of depressive symptoms.

This review concludes: "In conclusion, vitamin D deficiency may be associated with an increased risk or severity of depression. Supplementation of vitamin D may confer protection for depressed patients." The authors discuss mechanistic pathways and clinical data supporting that low vitamin D status is linked to more severe depressive symptoms and that correcting deficiency may help improve mood in some patients.

Anemia is described as causing fatigue, weakness, and shortness of breath, and the page notes that anemia symptoms may be similar to those of other diseases, which can make the cause of exhaustion harder to distinguish.

Micronutrients such as vitamin B12, vitamin D, folates, zinc, and selenium have been recommended for preventing maternal depression. Multiple micronutrients have been studied as potential adjuncts in depression, but the evidence base is heterogeneous.

This review found that vitamin D deficiency has the greatest evidence of an association with perinatal depression. The evidence for other micronutrients is mixed, inconclusive, or limited. The review provides evidence for routinely screening for vitamin D antenatally to enable supplementation and potentially reduce the risk of perinatal depression.

This meta-analysis on primary depression found that vitamin D supplementation reduced depressive symptoms in individuals diagnosed with depression (overall SMD −0.15, 95% CI −0.26 to −0.04). Subgroup analysis showed that vitamin D significantly lowered depressive symptom scores only when serum 25(OH)D levels were above 50 nmol/L, whereas it did not have a positive effect in those with primary depression and lower 25(OH)D levels. The authors interpret this as vitamin D being beneficial for depressive symptoms mainly when baseline levels are sufficient or repleted.

The page says iron-deficiency anemia can make people feel tired and lacking in energy, and that this may make them less productive, difficult to keep awake, or less able to exercise regularly.

Micronutrient deficiencies may play a contributory role in depression and anxiety, but the strength of evidence differs by nutrient. The most defensible clinical position is that micronutrient deficiencies should be screened for and corrected when present, especially in vulnerable populations, while continuing to manage depression and anxiety through standard psychiatric care.

The page says low iron stores can cause persistent fatigue, brain fog, headache, dizziness, shortness of breath with mild exertion, palpitations, and difficulty concentrating even when blood count is normal.

Emerging evidence in nutritional psychiatry shows that deficiencies in B-complex vitamins, magnesium, and other micronutrients can produce symptoms resembling depression, anxiety, ADHD, and psychosis.