After months at $250, the price of the digital currency bitcoin took flight in early November, peaking above $450 before falling back to $360 more recently. There is some evidence that trading in a bitcoin-linked fund, Bitcoin Investment Trust (GBTC), may have played a role in the spike.

On Oct. 21, for the first time since the fund’s May launch on the over-the-counter marketplace OTCQX, the spread between the publicly traded shares of the fund and the price of bitcoin became almost negligible, with the fund closing at a 1.9%...