Facebook’s global head of safety is set to testify before a Senate panel next week amid mounting concerns the social media platform can seriously damage young people’s mental health. Last week, The Wall Street Journal published a report based on internal Facebook documents revealing its Instagram app makes many adolescent users, particularly teenage girls, feel bad about themselves, and can lead them toward harmful content. The report also shows Facebook was aware of the negative impacts of the app but did not take any action to address the issue.