The co-deputy leader of the Greens quietly returned to work this week and will resume duties as a spokesperson for foreign affairs, defence and communications.

"I'm really glad to be back, and glad to be a part of this work," Ludlam said on a post on his Facebook page on Tuesday.

Ludlam thanks everyone who sent him messages of care and support over the past few months, including current and former parliamentarians "from across the political spectrum".

"I’ve had the benefit of a supportive family, an amazing team, access to healthcare and a workplace that makes allowance for illness of all kinds," Ludlam said.

"I am keenly aware that these advantages are not available to far too many people with mental illness. Treatment and professional care should be available to everyone who needs it."

BuzzFeed News understands he will be in Canberra for the first sitting session of the parliamentary year in February.