The article from The Economist that claims heavy use of social media is linked to mental illness is completely true. The article states "But they also said that the platforms exacerbated anxiety and depression, deprived them of sleep, exposed them to bullying and created worries about their body image and “FOMO” (“fear of missing out”). Academic studies have found that these problems tend to be particularly severe among frequent users". This claim of frequent issues of anxiety, depression and sleep deprivation line up with The National Library of Medicine's article on Link between excessive social media use and psychiatric disorders.
The story states "Social media use is the second leading cause of disability among psychiatric disorders". It also says "However, unrestrained use of social media can lead to the development of many psychosocial problems, such as disturbed sleep4–6, decreased subjective happiness7, and poor academic performance8,9, in addition to anxiety and depression6,10". This article explains how social media and mental illness directly coincide wth one another. When an individual has a problem with their mental health they often lean onto social media, and when one examines their mental illness it can often come from chronic social media use. Therefore proving the claim that heavy use of social media is linked to mental illness as true.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10129173/