This song is about the benzodiazepine, Xanax, hence the name. It’s typically used to treat certain anxiety disorders, such as panic disorder because of its strong sedative effect.
Throughout the music video you can see the lead singer, Josh Katz, experience moments of anxiety and self doubt.
He seems to call the sedative, Ana.
The singer looks as though he depends on it as he acknowledges throughout the song.
As well in the song, he does mention the pill Xanax.
The instrumental background also supports this, the music deliberately slows down to show how Xanax affects someone.