European share prices may have been supported since November by hedge funds covering their short positions, essentially a bet that an asset price will weaken, the bank said, noting that there was less buying of UK equity.
Trend funds, or CTAs, which frequently switch their buy and sell positions, have stayed bullish for longer than they usually would in European equities, the note said.
As well as closing bearish bets, some hedge funds have added long positions since February, although the bank questioned whether this trend would continue.
"The potential for cyclicals to keep getting bought as much as they have lately - by hedge funds at least - also seems unlikely," JP Morgan said.
Equity funds, multi-strategy funds and computer led and trend trading were among the hedge funds involved in covering short positions and establishing long positions, it said.