Addiction

Addiction was a dependency on a particular stimulus. According to the Twelfth Doctor, you couldn't tell if something was an addiction until you tried to give it up.

It was possible to be addicted to time travel. Following her "last hurrah", Clara Oswald was unable to give up travelling in the TARDIS and so chose to lie to the Doctor in order to stay. (TV: Mummy on the Orient Express)

Sarah Jane Smith accused a pair of Slitheen-Blathereen of being addicted to Rakweed, to which Leef Apple Glyn Slitheen-Blathereen denied, retorting that they "just lov[ed] it, that's all." (TV: The Gift)

Lucy Sobel's boyfriend Ricky was addicted to heroin. (PROSE: Slow Decay)