(CNN) - The Mona Lisa is arguably the world's most famous painting -- and yet, like many of Leonardo da Vinci's works, it's also considered unfinished. Half a millennium after his death, new research has identified a potential explanation behind the Renaissance artist's series of uncompleted projects: attention deficit hyperactivity disorder, or ADHD.
Researchers from King's College London and the University of Pavia in Italy consulted historical evidence, including accounts from Leonardo's contemporaries, and concluded that his issues with time management, concentration and procrastination could be attributed to ADHD.
Marco Catani, professor of neuroanatomy and psychiatry at King's College London, and Paolo Mazzarello, a professor in the University of Pavia's brain and behavior sciences department, said the disorder could explain "aspects of his temperament and the strange form of his dissipative genius."
"It would be historically incorrect to accept the biographical account elaborated by the Romantic authors of Leonardo as a solitary genius who remained unappreciated by his contemporaries owing to his ideas being too advanced for his time," they wrote.
"His most attentive biographers had always indicated that Leonardo tried hard to please customers that were inevitably left with the disappointment of being denied possession of a concrete expression of his talent. His contemporaries could never understand or forgive his lack of discipline, not his visionary mind."
The researchers highlighted Leonardo's tendency to switch "from task to task," as well as his habit of working continuously throughout the night, sleeping rarely and "alternating rapid cycles of short naps and waking."
They also noted that he was left-handed, and survived a left hemisphere stroke at the age of 65 with his language faculties intact. Both factors indicate a "reverse right hemisphere dominance for language," the researchers wrote, a trait present in less than 5% of the population.
Previous researchers have suggested Leonardo had dyslexia, a learning difficulty often diagnosed alongside ADHD, citing spelling errors and mirrored writing in his notebooks. "Atypical hemispheric dominance, left-handedness and dyslexia are more prevalent in children with neurodevelopmental conditions, including ADHD," Catani and Mazzarello wrote.
"Undeniably Leonardo accomplished more than any other human being could possibly dream of in a lifespan, but one wonders what would have been the impact of his work on history if he had managed to apply himself more consistently to his art and effectively disseminate his intuitions and discoveries," they concluded.
Louise Theodosiou, a spokesperson for the Royal College of Psychiatrists, told CNN that previous studies have linked ADHD with enhanced creativity. "While a symptom of ADHD is difficulty concentrating, people with ADHD can also focus intensely to the exclusion of all else on a narrow area," she said.
"This combined with the fact that people with ADHD may take risks or think outside the box can intensify creativity and productivity."
Highlighting positive characteristics associated with ADHD could help to challenge "negative perceptions" of the disorder, Theodosiou said. "Da Vinci is a positive and highly regarded figure whom people are likely to be keen to be compared to.
"However it is of note that there may be many people with ADHD who do not possess obvious creative skills," she added. "Thus it is possible that for a minority of people with ADHD, this may be another way in which they feel that they fail."
Graeme Fairchild, from the University of Bath's department of psychology, told CNN that the new research demonstrates that "people with ADHD can still be incredibly talented and productive, even though they might have symptoms or behaviors that lead to impairment such as restlessness, poor organizational skills, forgetfulness and inability to finish things they start."
The research could also challenge the misconception of ADHD as a condition only experienced in childhood, he said. "For many people, ADHD is a lifelong condition rather than something they grow out of, and it certainly sounds like Leonardo da Vinci had major problems in many of these areas throughout his life."
However, Fairchild challenged the researchers' suggestion that Leonardo's work was hindered by his possible ADHD. "Maybe the restlessness, energy and creativity that came with his ADHD explains why he achieved so much in so many different fields, even if he often didn't finish the things he started," he said.
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