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 ε2 was significantly lower in patients with MDD than in the controls, whereas no significant difference in apo ε4 allelic frequency between these two groups was found. Conclusion: The apo ε4 allele was not associated with MDD in this study. However, the finding of a lower frequency of the apo ε2 allele in MDD could lead to the conclusion that the apo ε2 allele likely provides a protective effect against MDD in the Taiwanese population.