Once again, the media taking a study and pushing a narrative with it.
From age 12 to 14 and 14–16 years, the interaction term between social media use and the intercept (i.e., overall level) of social anxiety was negative and significant, indicating that increased social media use forecasted a small decline in social skills among those with higher levels of social anxiety symptoms
So, there’s no overall relationship, except a negative one once you factor in an interaction term.
Theres also nothing here that says people who spend more time on social media are more mentally “healthy.” Just that they have more friends. Or do they use social media more because they have more friends? This isn’t some slam dunk for social media.