Exploring the link: Correlation between serum vitamin B12 and depression severity

INTRODUCTION

Depression, characterized by its heterogeneity in manifestation and etiology, presents a significant challenge in psychiatric epidemiology and treatment. It is now well established that various biological factors, including micronutrient levels, play a critical role in mental health. Among these micronutrients, vitamin B12 has garnered significant attention for its potential influence on emotional stability and neuropsychiatric disorders, particularly depression. Vitamin B12 is primarily found in animal-based foods such as meat, fish, eggs, and dairy, making vegetarians and vegans more prone to deficiencies. The recommended daily intake of B12 ranges from 2.4 to 2.8 micrograms. However, a vegetarian diet typically provides only about 0.5 μg/day, placing vegetarians, and especially vegans, at a higher risk for vitamin B12 deficiency.^[1] External supplementation, in the form of oral tablets or intramuscular injections, is essential for individuals with absorption issues (e.g., pernicious anemia and gastrointestinal disorders) or dietary restrictions.

It is a water-soluble vitamin, crucial for a range of physiological processes, including red blood cell production, DNA synthesis, and, more importantly, the optimal functioning of the nervous system.^[2]

One of the most critical roles of vitamin B12 in emotional well-being lies in its involvement in the methylation cycle. Vitamin B12 acts as a cofactor for the enzyme methionine synthase, which is necessary for the conversion of homocysteine to methionine. Methionine is subsequently transformed into S-adenosylmethionine (SAMe), which is an essential methyl donor involved in numerous methylation reactions, including those responsible for the synthesis of key neurotransmitters such as serotonin, dopamine, and norepinephrine.^[3] These neurotransmitters are integral to mood stabilization, stress response, and overall cognitive functioning. SAMe plays a pivotal role in neurotransmitter production by donating methyl groups necessary for the formation and activation of these chemicals in the brain.^[4]

Vitamin deficiencies can lead to homocysteinemia, which in turn lowers SAM levels, disrupting the metabolism of neurotransmitters, phospholipids, myelin, and receptors.^[5] This also results in the activation of NMDA receptors, endothelial damage, and increased oxidative stress.^[6] These neurotoxic effects play a role in the development of several psychiatric conditions, including depression, schizophrenia, and anxiety disorders. In addition, they contribute to neurological diseases such as dementia, Parkinson’s disease, cognitive impairments, cerebral atrophy, and epilepsy.^[7-10] The deficiency is also associated with mania, obsessive–compulsive disorder, and alcohol dependence, and is a recognized independent risk factor for stroke.^[11] Low serotonin levels are associated with feelings of sadness, anxiety, and irritability, which are hallmark symptoms of depression. In addition, vitamin B12 deficiency can hinder the synthesis of dopamine, a neurotransmitter associated with motivation and reward. Dopamine dysregulation has been strongly linked to the anhedonia and lack of motivation seen in depressive disorders.^[12]

Moreover, the conversion of dopamine to norepinephrine, another crucial neurotransmitter for the body’s response to stress, is also compromised in cases of vitamin B12 deficiency. Norepinephrine plays a key role in the fight-or-flight response, emotional stability, and cognitive function. Deficiencies in norepinephrine due to impaired vitamin B12-related pathways can exacerbate symptoms of depression, particularly those associated with stress management and resilience to emotional distress.^[13]

Thus, maintaining adequate vitamin B12 levels is essential not only for normal physiological functioning but also for the modulation of mood through its impact on neurotransmitter synthesis. Its deficiency can lead to a cascading effect that impairs multiple neurotransmitter systems, ultimately contributing to mood disorders, including depression. This interplay between vitamin B12 and neurotransmitter production suggests that sufficient B12 levels are crucial for emotional and psychological well-being.^[14]

Our research aims to systematically examine the correlation between serum vitamin B12 levels and the severity of depressive symptoms, quantified using the Hamilton Depression Rating Scale (HDRS), in a cohort of 120 individuals, including 60 patients with clinical depression and 60 matched controls. This case–control observational study seeks to provide empirical evidence on the role of vitamin B12 as a modulator of depressive symptoms, thereby offering insights into its utility as a biomarker for depression severity and potential therapeutic implications.

The study aimed to examine the correlation between serum vitamin B12 levels and depression severity measured by the HDRS in patients and healthy controls. The primary objective of the study was to compare vitamin B12 levels in 60 depressed patients with 60 healthy controls. It also assessed if lower Vitamin B12 levels are linked to higher HDRS scores.

MATERIAL AND METHODS

This study was conducted collaboratively between the Department of Psychiatry and the Department of Biochemistry after obtaining ethical clearance from the Institutional Ethics Committee at Acharya Shri Chander College of Medical Sciences, Sidhra, Jammu.

A total of 120 participants were recruited for the study, which included 60 patients diagnosed with clinical depression and a control group of 60 healthy individuals.

Sixty patients having a confirmed diagnosis of depressive disorder were evaluated using a comprehensive evaluation based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), done by a psychiatrist, and the results were further validated by a second psychiatrist who conducted an independent evaluation using the same structured interview based on DSM-5 criteria. Inpatients as well as outpatients were included for the same.

The healthy control participants were subjected to structured interviews regarding the presence of any psychiatric symptoms. This assessment aimed to ensure that the control group was free from any psychiatric conditions that could potentially confound the study results.

Depression Severity Assessment: The severity of depressive symptoms among participants was assessed using the HDRS17. Informed consent was obtained from all participants.

Vitamin B12 measurement: Serum vitamin B12 levels were measured in all participants using standard biochemical assays. It was done using the electrochemiluminescence immunoassay (ECLIA) technique. It was done using cobas e immunoassay analyzers.

The serum vitamin B12 levels were categorized as <200, 200–400, and >400 to make it easier to classify and analyze. Furthermore, previous researches were used as the basis for this classification.^[15,16]

RESULTS

In our investigation into the correlation between vitamin B12 levels and depression severity, we employed a comprehensive approach encompassing demographic factors, vitamin B12 levels, and depression severity as quantified by the HDRS. This study was conducted on 120 participants, comprising 60 patients diagnosed with clinical depression and 60 healthy controls.

Vitamin B12 levels and depression

The analysis of vitamin B12 levels revealed a notable variance between patients and controls. In the patient group, a substantial proportion (65%) had vitamin B12 levels below 200 pg/mL. Conversely, in the control group, the majority had higher vitamin B12 levels, with 28 individuals (46.67%) in the 200–400 pg/mL range and 20 individuals (33.33%) exceeding 400 pg/mL. The chi-squared test confirmed a significant association between vitamin B12 levels (Chi-square value = 24.87) and the presence of depression (P = 3.98 ×10⁻⁶). It can be observed that patients with lower vitamin B12 levels (<200 pg/mL) predominantly had higher HDRS scores [Figure 1].

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Figure 1:

Vitamin B12 levels in patients and controls.

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The Pearson correlation coefficient r is approximately −0.836, indicating a strong negative correlation between vitamin B12 levels and HDRS scores. This means that lower vitamin B12 levels are associated with higher HDRS scores, suggesting that vitamin B12 deficiency is strongly correlated with more severe depressive symptoms [Figure 2].

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Figure 2:

Correlation between HDRS scores and vitamin B12 levels. HDRS: Hamilton depression rating scale.

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Vitamin B12 levels and age: The correlation coefficient r was −0.026, indicating a very weak negative correlation between age and vitamin B12 levels in our data. A scatter plot was created to assess the linear relationship between age and vitamin B12 levels [Figures 3 and 4]. A linear trendline was fitted to the plot, and the coefficient of determination (R²) was calculated. The R² value was found to be 5.76 × 10⁻³, indicating a very weak correlation between age and Vitamin B12 levels. This suggests that age does not significantly explain the variation in vitamin B12 levels within the study population.

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Figure 3:

Scatter plot- age and vitamin B12 levels in patients.

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Figure 4:

Scatter plot - age and vitamin B12 levels in controls.

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DISCUSSION

Our findings suggest a significant association between lower vitamin B12 levels and increased severity of depressive symptoms. The marked difference in vitamin B12 levels between patients with clinical depression and healthy controls underscores the potential role of this micronutrient in modulating depressive symptomatology. While the demographic factor of age showed a weak positive correlation with depression in our cohort, the strong link between vitamin B12 deficiency and higher depression scores, as assessed by HDRS, provides compelling evidence for the consideration of vitamin B12 levels in the evaluation and management of depression.

These results contribute valuable insights into the complex interplay between micronutrient status and mental health, particularly in the context of depression. It highlights the potential of vitamin B12 as a biomarker for depression severity and underscores the importance of considering nutritional factors in psychiatric evaluations and treatment strategies. Further research is warranted to explore the causative aspects of this association and to evaluate the therapeutic implications of vitamin B12 supplementation in depressive disorders.

Our study reveals a strong association between vitamin B12 deficiency and depressive symptoms. This finding aligns with the existing body of literature that emphasizes the link between micronutrient deficiencies, particularly vitamin B12, and depressive disorders.

Consistent with our results, Hintikka et al. (2003) reported a positive association between higher vitamin B12 levels and improved treatment outcomes in depression.^[17] In contrast, Lundin et al. (2014) found no significant correlation between baseline vitamin B12 levels and depression severity in treatment-resistant major depressive disorder and bipolar depression patients.^[18] This disparity may suggest that the impact of vitamin B12 on depression could vary across different types of depressive disorders or stages of treatment resistance.

Our study further corroborates findings from Seppälä et al.^[19] (2013), who observed lower mean vitamin B12 levels in individuals with melancholic depressive symptoms, and Resler et al. (2008), who showed significant improvement in depression scores with fluoxetine and folic acid treatment.^[20] These studies collectively reinforce the potential role of vitamin B12 in depression.

Interestingly, while our study observed consistent vitamin B12 levels across different age groups and sexes in both depressed patients and healthy controls, Penninx et al.^[21] (2000) reported a different trend. In their study on older, physically disabled women, they found a significant age-related fluctuation in vitamin B12 levels, with 27% of severely depressed women showing vitamin B12 deficiency compared to 14.9% in the non-depressed group. In addition, they noted that women with vitamin B12 deficiency were more than twice as likely to experience severe depression. This contrast highlights that while our population exhibited uniformity in Vitamin B12 levels across age groups and sexes, the Penninx study points to an increased vulnerability to depression linked to vitamin B12 deficiency, particularly in older adults.^[21]

Moreover, Zhao et al. (2023) highlighted an association between low serum levels of folate, vitamin B6, and vitamin B12 with cognitive impairments in depression patients.^[22] This association bolsters our observation of lower B12 levels correlating with higher HDRS scores and points to a broader impact of vitamin B12 deficiency on various aspects of depressive pathology.

CONCLUSION

In summary, our research contributes significantly to the understanding of vitamin B12’s role in depression, supporting its potential as a biomarker for depression severity. It emphasizes the importance of considering micronutrient levels in the comprehensive management of depressive disorders and advocates for heightened clinical awareness and further research into the therapeutic potential of vitamin B12 supplementation in depressive disorders.