Autism

Sarah Jane Smith's granddaughter Lily was autistic. This manifested in many ways, including her tendency to scream when prevented from doing something she loved, such as playing in the snow, or her habit of attacking other children or simply hitting them. (PROSE: Lily)

Ryan Scott, who was also autistic, would sing to isolate himself from the world. (PROSE: Into the Silence)

Olivia Jennings thought that the Sixth Doctor might be autistic. (AUDIO: The Curious Incident of the Doctor in the Night-Time)

Behind the scenes
Chris Chibnall wrote the Thirteenth Doctor with the intent that they would share many of the same traits as those who were on the autism spectrum.