Get sectioned

Martha Jones told the Tenth Doctor that she would get sectioned if she were tell her friends back in her own time that she had seen William Shakespeare in 1599. The implication was that her friends would think her crazy. (TV: The Shakespeare Code)

Behind the scenes
Though not spelled out precisely in a DWU narrative, the expression is a British English-only synonym for to be committed to a mental institution. Its meaning comes from the fact that provisions for state action on mental health grounds derives from various sections of law.