Snap stock is down more than 3.7 % on Thursday after Cowen analyst John Blackledge downgraded it from outperform to market perform.

Blackledge also decreased his price estimate from $75 to $45 for the stock. Snap's stock is now trading at roughly $41.

In a note to investors, the analyst expressed concerns about Apple's iOS 14.5 changes, which could affect the company's analytics, such as measurement, targeting, and attribution, in connection to ad units.Snapchat Screenshots | Copyright Infringement | Gestalt Law

In the first half of this year, the company will face difficult comparisons, since its current valuation remains high.

The company's January 2020 upgrade to outperform was based on "multi-year proprietary tests showing increased adoption of SNAP's direct response (DR) advertising units, which currently account for >50 % of ad revenue," according to Blackledge.

"The 3Q21 print revealed that SNAP DR was not immune to unfavorable consequences of iOS 14.5 / IDFA adjustments, and we are concerned SNAP may have to continue to navigate through them in the coming quarters," he said.