Citing documents found by Germany's air transport authority, the "Bild am Sonntag" tabloid said doctors at Lufthansa wrote that "Lubitz should continue to receive psychological treatment, even though he was deemed fit to fly" by an independent expert in 2009, after interrupting his flight training.
Lubitz has been blamed for the crash of Germanwings flight 4U9525 on March 24, which killed all 150 people on board. Investigators believe the co-pilot deliberately brought the Airbus A320 down in the French Alps, en route from Barcelona to Düsseldorf.
German prosecutors have also said Lubitz was diagnosed as suicidal "several years ago," before he became a pilot.
The latest report does not specify if Lubitz had indeed benefited from continued treatment, however.
Aviation regulator unaware
Last week, Germany's national aviation regulator said it was unaware that Lubitz had struggled with severe depression before the disaster, and was only able to examine his medical files three days after the crash.
A spokesman for the Federal Aviation Office (LBA) told the AFP news agency that Lufthansa, Germanwings' parent company, had provided "no information about the medical background" of 27-year-old co-pilot.
Whilst receiving treatment from neurologists and psychiatrists, Lubitz was reported to have appeared more stable of late.
During investigations at his Düsseldorf apartment, however, police found torn-up sick notes from a number of occasions, including the day of the crash.
The flight's second recorder, found last week, supported data recovered from the first black box, which suggested Lubitz had deliberately brought about the crash. He is suspected of locking the captain out of the cockpit.