Running back Daniel Thomas returned to practice Tuesday for the first time since sustaining his second concussion in a month.

Thomas said he passed the NFL-mandated cognitive tests Monday, and will now practice and play with an oversized helmet designed to minimize trauma to the brain.

The Dolphins held Thomas out of the game that followed each of his concussions, and coach Joe Philbin told reporters Monday that, “Whatever the medical people say, we’re going to do.”

Head injuries — and the way they’re treated by NFL teams — have been under a microscope in recent years, fueled by a series of federal negligence lawsuits filed by thousands of former players.

They claim the league knew of the potential long-term health risks of repeated head trauma — including memory loss, migraine headaches and depression, sometimes leading to suicide — but until recent years did little about it. The league disputes those accusations, and is expected to fight the suits all the way through trial, should they reach that far.

When asked if he was concerned about the potential long-term risks associated with multiple concussions, Thomas said, “not at all.”

“You’ve just got to keep playing,” he said. “You can’t worry about them. I’m not a doctor, so you’ve got to ask [them].”

Dr. Gillian Hotz, the director of the concussion program at the University of Miami’s Miller School of Medicine and one of the nation’s leading research neuropsychologists, cautioned that there isn’t a universal guideline to know how a particular player might be affected.

“If you’ve had one, you’re at high risk to have others,” Hotz said. “But we don’t have a crystal ball. Nobody knows how many hits somebody really can take. Every brain is wired different.”

League rules prohibit any player who sustains a concussion from returning to a practice or game that same day. Furthermore, the concussed player cannot participate in football activities until he is fully asymptomatic.

However, there are no rules stipulating how many concussions a player can sustain before being shut down for a season, or for good.

Bush eyes prize

Even after being held to fewer than 70 yards in each of the past four games, Reggie Bush hasn’t given up on his goal of leading the league in rushing.

“Yeah, I think it’s still possible,” Bush said. “It’s not my focus. It’s obviously a goal, but it’s not my focus while I’m out there.”

Through six weeks, Bush ranks 12th in the NFL with 434 yards, 157 behind league-leader Jamaal Charles of Kansas City.

THIS AND THAT

•  Richard Marshall (back) and Jimmy Wilson (undisclosed) were held out of Tuesday’s practice.

•  Ryan Tannehill has been nominated for NFL Rookie of the Week honors after his two-touchdown, no-interception performance Sunday against the Rams. Those interested in voting for Tannehill can do so at NFL.com.

• The Dolphins have added Joe Holland, a rookie linebacker from Purdue, to their practice squad, cutting Louis Nzegwu to make room.

• Philbin, Green Bay’s former offensive coordinator, on Packers quarterback Aaron Rodgers’ six-touchdown performance Sunday against Houston: “I watched a couple of throws and thought, ‘They’re not missing Philbin.’ ”

• Philbin and the entire team spent Tuesday afternoon beautifying Barbara Hawkins Elementary School in Miami Gardens. They planted flowers, laid stones and mulch and painted in the school’s Butterfly Garden, and also decorated the teachers’ lounge.

•  Todd Bowles, the Dolphins’ interim coach after Tony Sparano’s dismissal last year, is the new defensive coordinator of the Philadelphia Eagles. He replaces Juan Castillo, who was fired Tuesday.