Criminal Minds dropped its Spencer Reid drug addiction arc, and many viewers wondered why. An original member of the FBI's Behavioral Analysis Unit (BAU) in the show, the character (played by Matthew Gray-Gubler) was known for his smarts. But, Reid's life wasn't a walk in the park; while all characters on Criminal Minds went through a lot, he's arguably had the most traumatizing experiences among them. Throughout his 15-season arc on Criminal Minds, Reid was in several near-death experiences.
https://screenrant.com/criminal-minds-reid-drug-addiction-story-end-reason/