Protective effect of the apo ε2 allele in major depressive disorder in Taiwanese

Objective: Major depression is an important comorbidity in Alzheimer's disease, which is definitely associated with the apolipoprotein E (apo E) polymorphism. The aim of this study was to explore the role of the different apo E polymorphisms in major depressive disorder (MDD) in a Taiwanese population. Method: We examined apo E genotypes in 273 Taiwanese patients with MDD and 429 healthy community controls, and compared their polymorphism distribution. Results: The allelic frequency of apo epsilon 2 was significantly lower in patients with MDD than in the controls, whereas no significant difference in apo epsilon 4 allelic frequency between these two groups was found. Conclusion: The apo epsilon 4 allele was not associated with MDD in this study. However, the finding of a lower frequency of the apo epsilon 2 allele in MDD could lead to the conclusion that the apo epsilon 2 allele likely provides a protective effect against MDD in the Taiwanese population.