The Seagulls went into the game having scored only four goals in their previous five matches and, in a lively start, former Newcastle winger Kazenga LuaLua provided an immediate threat for the Seagulls.
LuaLua forced goalkeeper Karl Darlow into a scrambling save in only the third minute after being fed by Stephen Ward, and two minutes later he fired an angled shot over the crossbar from inside the area.
Darlow later dived to hold a bouncing 30-yard drive from Ashley Barnes before Forest came close to breaking the deadlock.
Kuszczak was alert again midway through the first half when he beat away a firm drive from fellow countryman Radoslaw Majewski.
Lansbury and Reid both put shots wide for Forest before Wales international midfielder Andrew Crofts fired Brighton ahead in the 31st minute from close in.
Crofts pounced after a deep cross by Ward was mis-hit by Barnes and the ball ran kindly into the path of the Welshman.
Crofts was playing through the pain barrier for the injury-plagued Seagulls after pulling out of the Wales squad, having initially been named for the World Cup qualifiers against Macedonia and Belgium later this month.
Forest almost replied straight away through midfielder Nathaniel Chalobah,whose rasping shot was parried by keeper Kuszczak.
The visitors were on terms within 60 seconds of the restart, midfeilder Lansbury rising to level with a superb header from eight yards following a corner from Majewski.
Darlow prevented Brighton from regaining the lead only three minutes later by pushing a goal-bound shot from Barnes onto the post.
Two goals in the space of two minutes put Forest firmly in charge with a strike from Henderson and a spot-kick by Lansbury boosting the visitors.
Henderson put his side ahead with a left-foot shot into the bottom corner on the hour after Matt Upson could only partially clear a cross by Danny Collins.
Then Brighton captain Gordon Greer brought down striker Simon Cox and Lansbury stepped up to blast his second goal from the spot.
Forest were reduced to 10 men after 67 minutes when Chalobah, booked earlier for a foul, received a second yellow for a push on LuaLua.
LuaLua had a curling free-kick saved by Darlow as the Seagulls struggled to launch a late fight-back.