You are paying for a completely different regulatory framework
A meta-analysis of 16 clinical trials (N=6,276) did not find a significant effect of vitamin supplementation on depressive symptoms.38 However, a review of five clinical trials (N=6,507) by da Silva and colleagues found that supplementation with folic acid, vitamin B6, and vitamin B12 was effective in preventing depression in patients recovering from stroke.39 Supplementation with folic acid, vitamin B6, and vitamin B12 may improve symptoms of depression and bipolar disorder among patients with these disorders by increasing the absorption and utilization of mood-stabilizing medications.35 Hyperhomocysteinemia is also associated with an increased risk of schizophrenia
A diet that includes processed foods, especially those that are imported from foreign countries and not organically grown (and even plant foods grown in soil that has high levels of metals), can also be a contributing factor
Without a bacteriostatic agent like benzyl alcohol, any microbe that enters the vialfrom the air, the vial stopper, or the syringe needlecan multiply unchecked