Dear Editor,We read with great interest the article by Wang and He entitled ‘Levels of serum brain-derived neurotrophic factor in Type 2 diabetes mellitus patients with and without depressive symptoms’ in which the investigators reported that the serum brain-derived neurotrophic factor (BDNF) level was lower in Chinese Type 2 diabetes mellitus patients with or without depressive symptoms than that in healthy controls [1].However,we think there are some points that should be discussed.