The Seattle Seahawks lead the NFL in suspensions for performance-enhancing drugs since Pete Carroll became coach in 2010, research by ESPN Stats & Information shows.

Defensive end Bruce Irvin's four-game suspension, announced Friday, was the fifth during that span, according to research ESPN's Steve Martinez conducted using STATS PASS.

2010-13 PED Suspensions

The total does not include the 2012 suspension implicating cornerback Richard Sherman, who overturned a four-game ban on appeal. The botched handling of a leaky collection cup proved critical to the successful appeal.

Seven other teams have incurred three or four substance-abuse suspensions for PEDs over that span, including the Denver Broncos and New York Giants with four apiece, according to STATS PASS. The San Francisco 49ers are among 10 teams with zero.

Since 2010, the NFL suspended Seattle's Irvin, Brandon Browner, Winston Guy, Allen Barbre and John Moffitt for PED usage under its policy on anabolic steroids and related substances.

Moffitt said he took Adderall, a psychostimulant prescribed for attention-deficit disorders, under a doctor's prescription without knowing he needed a special exemption from the NFL.

Sherman, who denied violating the policy, has suggested doctor-approved Adderall use is widespread. He called for the NFL to lift its ban on the substance.

The chart ranks NFL teams by most PED-related suspensions since Carroll arrived as the Seahawks' head coach on Jan. 12, 2010.

Carroll and the NFL denied a 2009 report linking former USC players to positive steroid tests. One of the players named in that disputed report, Brian Cushing, later served a four-game NFL suspension for violating the policy on anabolic steroids and related substances.

First-time violators of the policy receive four-game suspensions. The penalty doubles for second-time violators. Third-time violators face suspensions of at least 12 months, subject to reinstatement at the commissioner's discretion. Players suspended under the policy for any length become ineligible for the Pro Bowl or any other NFL or NFL Players Association honors.

NFL policy requires annual testing for steroids and related substances when training camps begin or whenever a player reports to the team after camps begin. Preseason and regular-season protocol calls for 10 players per team to be tested at random each week. That protocol continues into the postseason for playoff teams. Players under contract can be tested up to six times during an offseason, subject to increases following a positive test.