Response to Letter by Vale
We thank Dr Vale for his comments on our study. He raises an interesting question as to whether deregulated stress response could be an underlying mechanism for the association between depressive symptoms and risk of stroke. As we stated in our article, the biological pathways by which depressive symptoms are associated with stroke risk remain unclear. Do psychological factors act to augment stroke risk or are they the result of a subclinical cerebrovascular process evident on brain MRI1? Dr Vale has suggested a plausible mechanism not considered in our discussion: namely, that there is a subgroup of depressed individuals who react to mental stress with intense immune activation thus making them more prone to atherosclerosis. He proposes that it may be worthwhile to measure salivary α-amylase, which has been shown to be elevated at times of psychological stress in healthy adults. However, increased levels of salivary α-amylase have not been demonstrated prospectively to be associated with increased incidence of stroke or other cardiovascular disease. We thank Dr Vale for bringing this novel hypothesis to our attention.