PURPOSE OF REVIEW: This study aims to analyze the effects of vitamin D on serotonin synthesis, release, and function in the brain, and to explore its relationship with various psychiatric disorders. RECENT FINDINGS: The hormone calcitriol plays a vital role in regulating a multitude of biological processes within the human body. Its deficiency can lead to significant adverse effects on overall health and well-being, including physical and psychological consequences. Evidence indicates that vitamin D may exert influences through receptors in the brain, modulating serotonin production and influencing emotional and cognitive processes. Recent studies propose that elevated serum vitamin D may enhance mood and alleviate depressive states. The impact of vitamin D on cognitive function and behavior remains an area of ongoing investigation. This literature review analyses the available evidence on how vitamin D intake impacts the severity of illness and medication requirements in diverse psychiatric disorders. A review of the literature suggests that there may be a correlation between vitamin D and serotonin, which could potentially contribute to more favorable outcomes in the context of illness. Vitamin D may increase the amount of serotonin in the synaptic gap, which is the intended use of selective serotonin reuptake inhibitors (SSRIs), with its effect on the increase in serotonin release. According to reports, vitamin D supplementation in conjunction with SSRI group medication provides an additive effect for the management of psychiatric disorders.