"[2] "Sick Boy" was described as "a song about self-identity in today's world and standing tall in the face of what you can and can't control" in press materials.

[5] Kat Bein of Billboard opined that the song "sounds like a big departure from the New York City duo's usual romantic pop flair".

[7] Madeline Roth of MTV News regarded the song as "a catchy but gloomy slice of pure pop that sounds more like Twenty One Pilots than anything on their 2017 debut album, Memories...Do Not Open".

Comparing to party tracks like "Don't Let Me Down", he noticed the song of being "darker in tone", describing it as "downright gloomy", which strays away from their "wistful and melancholy" style.

[1] Derrick Rossignol of Uproxx wrote: "Musically, it strays further away from their EDM roots and more towards the successful pop sound they've developed for themselves, albeit with a more aggressive edge this time around.