Cushing can participate in preseason practices and games.
"We were disappointed to learn that Brian has been suspended for the first four games of the 2010 season," Houston general manager Rick Smith said in a statement. "Brian is a productive member of our team and this is a significant loss, but we have to be prepared to win without him."
Cushing, the 15th overall pick in last year's draft out of Southern California, had 133 tackles in 2009. The Texans finished 9-7 last season for their first winning record thanks in part to the improvement of a young defense that features Cushing, star middle linebacker DeMeco Ryans and 2006 top overall pick Mario Williams.
Veteran Kevin Bentley, who appeared in each game for Houston last season but never started, is Cushing's backup at outside linebacker.
Cushing was hounded by rumors of performance-enhancing drug use before he became a pro, but the Texans were undeterred. They said then they found no truth to those rumors in their draft preparations.
"I've passed every drug test out there and still have," Cushing said during his 2009 draft press conference. "I'm not that kind of guy."
Cushing had been promoting an appearance on the NFL Network show Total Access Live scheduled for Friday evening on his Facebook page before posting the following message Friday afternoon: "Had to cancel NFL Network and all other interviews due to a family emergency. Heading to airport to fly back to NJ to be with the fam."
Cushing did not provide any further details about the emergency. He is from New Jersey and had been in school in California this week.
The suspension was first reported by ESPN.