Depression is a not a simple term but has been used to describe a variety of infirmities, ranging from minor to debilitating. It is characterized not only by disheartened mood but also by a group of somatic, cognitive, and motivational symptoms. It is a multi-symptom disease and can even lead to suicidal attempt. There is currently no way to determine which antidepressant will work best for a given patient. Moreover, no one knows why some patients recover and others have no improvement, even after they spend months trying a series of medications. In fact, little is known with absolute certainty about how antidepressants improve mood, which means that many people continue to suffer while their doctors try a series of medications. Case control studies have supported a relationship between low folic acid, low vitamin B12, low vitamin D and high homocysteine (tHcy) levels as possible predictors of depression. The results from epidemiological studies are mixed and largely from elderly populations. Majority of the studies relating vitamin D status with depression are based either on a small sample size or non-representative of the local population. Clinical studies suggest that vitamin D, vitamin B12, folate and high tHcy level are involved in the pathophysiology of depression, anxiety and sleep disorder. We designed a study to determine relationship, if any, between vitamin D, vitamin B12, folate deficiency and high tHcy levels with depression, anxiety and sleep disorder in our local population. Total of 250 diagnosed patients of 18-75 years of age were enrolled for this study, after a written consent. Out of 250 patients, 150 patients were diagnosed as depressed, 50 as anxiety and 50 as sleep disorder. Depressed patients were further categorized into three groups depending on severity of disease i.e; mild, moderate and severely depressed patients. Blood measures included serum vitamin D, folic acid, vitamin B12 and tHcy levels and data was recorded on structured data collection form. The present study was conducted to assess whether serum levels of vitamin D, tHcy level vitamin B12 and folate are associated with depression, anxiety, sleep disorders and with severity of disease. It was observed that elevated depressive symptoms were associated with low vitamin D status, low folate and high tHcy status in all males and females. We also observed negative correlation of vitamin D and a significant positive correlation of tHcy in depression, anxiety and sleep disorder and with severity of disease in all males and females. It was concluded that low vitamin D, low folic acid and high serum tHcy levels, are correlates of depressive symptoms in our local population. The effects of vitamin D and tHcy are overlapping but distinct in our study. An association between serum folate, vitamin D, tHcy and cognitive impairment are of considerable public health importance in view of the increasing numbers of elderly people in Pakistani population. A plausible hypothesis for these association is that high tHcy levels cause cerebral vascular disease and neurotransmitter deficiency, which cause depression of mood. Furthermore, inadequate levels of either vitamin can lead to elevated plasma tHcy levels, which may be independently associated with Alzheimer’s and depression, thus raising interest in these vitamins as a means of prevention.