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)

Sarah Jane almost got married in The Sarah Jane Adventures but never had any kids of her own, she instead adopted two kids first Luke and then Sky. This creates a paradox because Sarah Jane had a funeral in Farewell Sarah Jane video on YouTube and there was no mention of a significant other of Sarah Jane.