New scans performed by the National Museum of Norway have confirmed that a hidden message on Edvard Munch’s The Scream was put there by the artist himself.

Created in 1893 under the original title Der Schrei der Natur (The Scream of Nature), the painting of a man apparently in agony has become one of the most well-known works in the world.

Munch had been on a walk when he got the inspiration for the painting, seeing vivid red lights in the sky, possibly caused by an eruption of Krakatoa.

“I was walking along a path with two friends – the sun was setting – suddenly the sky turned blood red – I paused, feeling exhausted, and leaned on the fence – there was blood and tongues of fire above the blue-black fjord and the city," he said of the painting. "My friends walked on, and I stood there trembling with anxiety – and I sensed an infinite scream passing through nature.”

At the top left-hand corner of the painting, there is a small message, written in pencil after the work was finished:

"Can only have been painted by a madman".

Ahead of an exhibition at the museum in 2022, the painting was analyzed using infrared technology to try to figure out who left the inscription. Over the decades, it's been suggested that it could have been written as an act of vandalism by somebody, or by Munch himself. By comparing the handwriting with his notes, they were able to confirm that it was written by the artist.

"The writing is without a doubt Munch’s own," curator at the National Museum Mai Britt Guleng said in a statement. "The handwriting itself, as well as events that happened in 1895, when Munch showed the painting in Norway for the first time, all point in the same direction."

The museum believes that the inscription was likely made after the painting was first exhibited in Kristiania (later to become Oslo). People at the time began speculating on Munch's mental health, with one medical student Johan Scharffenberg claiming Munch's paintings proved he wasn't of sound mind, to which the inscription may have been a response.

"I inherited two of mankind's most frightful enemies—the heritage of consumption and insanity—illness and madness and death were the black angels that stood at my cradle," Munch once wrote of his own mental health and the mental illness that ran through his family, including his much-beloved sister.

"My fear of life is necessary to me, as is my illness," he added. "Without anxiety and illness, I am a ship without a rudder....My sufferings are part of my self and my art. They are indistinguishable from me, and their destruction would destroy my art."