A 2-1 reverse at the Emirates Stadium means Arsenal have gone nine games without a win, a streak not matched since 1977.
Ljungberg replaced Unai Emery on an interim basis after the Spaniard was sacked last week, but has so far been unable to address an alarming slide in form.
Arsenal have not won since October 24 and Ljungberg admits confidence is rock bottom as he looks to turn things around heading into the packed Christmas schedule.
“They look very short on confidence,” he said.
“In the first half they were scared to get the ball and a bit scored to move, they were just standing still.
“That’s something we need to talk about. They need to have a win, we need to dig out a win and get them some confidence.
“They can do it because they showed it in the beginning of the second half and they did it really well for 20 minutes.
“It’s hard to say that when you lose at home, but they were very good in that little spell.”
For Brighton, this was a first-ever victory away to Arsenal and a maiden win on the road against an established “top six” opponent.
It also meant boss Graham Potter was able to repeat his Europa League triumph over the same opposition at the Emirates with Swedish minnows Ostersunds in February last year.
“Thursday nights at Arsenal are great!” smiled Potter.
“Hopefully the Premier League will arrange more games on a Thursday.”
Brighton’s second away win of the season lifted them above Aston Villa, West Ham and Bournemouth into 13th.
Potter added: “We showed great quality and great courage, so overall I’m delighted with the players. It’s fantastic to get three points and play like we did.
“Given the quality up front they have, everything can change, but credit to the players, they managed the situation well, and there was a bit of quality from us as well.
“We’ve had a tough batch of games so it’s nice to come away from home, win, and play well. It gives us a bit more confidence on the path to going somewhere.”
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