Mario's 'Depression (Thinkin' Of U)' stands as a defining track from his early career, capturing the raw emotional vulnerability characteristic of his debut era. Released alongside hits like 'Start Over, Hangover' and 'How Do I Breathe (Remix),' the song exemplifies the melancholic pop-rock sound that became his signature. The recording features a stripped-back arrangement that emphasizes the lyrical narrative of personal struggle and longing, resonating deeply with listeners during the mid-2000s. As a key component of his discography, the track highlights Mario's ability to blend acoustic guitar textures with emotive vocals, establishing a template for future releases that explored themes of heartbreak and introspection within the indie pop landscape.