The best text structure to use in an article discussing how social media can affect a person's mood would be cause and effect. This structure allows you to clearly outline how specific aspects of social media, such as exposure to positive or negative content, online interactions, or social comparison, can lead to various emotional outcomes.
Using cause and effect will enable you to analyze the connection between social media usage and changes in mood, helping readers understand the direct influence social media can have on their emotional well-being. You can also incorporate elements of description to elaborate on specific examples and experiences, but the primary framework of the article would benefit most from a cause and effect structure.