Leonardo da Vinci was dyslexic, and often wrote backwards.
"Dyslexia is a learning disorder characterized by difficulty reading due to problems identifying speech sounds and learning how they relate to letters and words. Also called specific reading disability, dyslexia is a common learning disability in children.
Dyslexia occurs in children with normal vision and intelligence. Sometimes dyslexia goes undiagnosed for years and isn't recognized until adulthood.
There's no cure for dyslexia. It's a lifelong condition caused by inherited traits that affect how your brain works. However, most children with dyslexia can succeed in school with tutoring or a specialized education program. Emotional support also plays an important role."
"Dysgraphia affects a person’s handwriting ability and fine motor skills.
A person with this specific learning disability may have problems including illegible handwriting, inconsistent spacing, poor spatial planning on paper, poor spelling, and difficulty composing writing as well as thinking and writing at the same time."
Writing backwards is a form of encryption but is not attributed to the disorder.