President Donald Trump may be more of a market bull than any president since Calvin Coolidge, but new findings from Bank of America Merrill Lynch suggest he might want to rethink his approach.

With the caveat that correlation is not causation, it appears that the more Trump tweets, the more nervous the stock market gets.

That at least was the finding of research by Bank of America Merrill Lynch.

Their investigation found that on days when Trump tweets more than 35 times, markets have seen negative returns. On days when Trump tweets fewer than 5 times, markets have seen positive returns.

It doesn't appear to matter what Trump is tweeting about, just the fact that he is being active on social media is enough to put the markets on edge.

The study looked at data since 2016. Days with more than 35 tweets are in the 90th percentile, while days with fewer than 5 tweets are in the 10th percentile. The negative returns on high-tweet days have been -9 basis points, while the positive returns on low-tweet days have been only +5 basis points.

So, if he really wants the stock market to go higher, perhaps Trump should seek to emulate his taciturn predecessor.

Jim Cramer and the AAP team are looking at everything from earnings and tariffs to the Federal Reserve. Find out what they're telling their investment club members and get in on the conversation with a free trial subscription to Action Alerts Plus.