Low folate levels combined with a MTHFR C677T mutation are an important cause of high homocysteine levels that have been found to be linked with major depressive disorder (MDD). Patients diagnosed with MDD were screened to find the folate level to be lower in this group when compared to controls. Low folate levels also correlated with an increased BMI, especially in females. BMI was found to be higher in MDD patients, which was associated with the MTHFR C677T mutation and increased homocysteine levels. This study reinforced the importance of folate intake being above recommended intakes for those with altered function of the methylation pathways, as it leads to elevated homocysteine levels that significantly impact on the development of diseases such as MDD.