Police are currently investigating the circumstances surrounding Carson’s injury, which ruled him out of Good Friday’s home win against relegation rivals Cheltenham.
A club statement read: “York City Football Club can confirm that Josh Carson was involved in an incident last Saturday evening.
“As a result, Josh was admitted to hospital on Sunday morning with what has now been determined as severe concussion.
“The 21-year-old has since been discharged from hospital.
“The club will not be making any further comment as the matter is now subject to a police investigation.”
Carson, a full Northern Ireland international, played the full 90 minutes during York’s 4-1 win at Mansfield last Saturday.