I hardly ever hear the word “overdose” by itself anymore, as in “so-and-so died of an overdose.” It’s always “so-and-so died of an accidental overdose.”
Isn’t that redundant? If you want to put it that way, wouldn’t the only alternative be an intentional overdose? Which would be a suicide.
The word “overdose” implies accidental. Someone tried to make themselves feel better in a high-risk way and miscalibrated.
So it’s either a suicide or an overdose, not an “accidental overdose.” End of story.