From: Ann Shumelda Okerson <[log in to unmask]>
Date: Fri, 16 Sep 2016 00:15:40 -0400

From a recent Elsevier newsletter:

"Based on our close review of the available evidence, there is no
clear citation advantage for open access articles, or at least not one
that can be identified as solely being related to an article’s access
status.  Whilst early studies suggested a causal relationship between
article OA status and higher citation counts, subsequent studies
identify weaknesses in the methodology used in earlier studies where a
citation advantage had been found."

https://www.elsevier.com/connect/citation-metrics-and-open-access-what-do-we-know