Nature Reviews Neuroscience (2020) https://doi.org/10.1038/s41583-019-0255-9 Published online 8 January 2020

In the originally published version of this article, the competing interests statement indicated that the authors had no competing interests; however, this statement was incorrect. The statement should have read as follows: ‘T.W.-C. is a co-founder, shareholder and paid consultant of Alkahest, Inc., a company that develops treatments for CNS diseases based on the concept that circulatory factors regulate brain function. J.V.P. declares no competing interests.’ This error has been corrected in the HTML and PDF versions of the article.