Link between reading news and deteriorating mental health? Given the prevalence of negativity and sensationalism in the news, I suspect individuals are also varyingly susceptible to (worsening) mental health issues arising from prolonged exposure. Perhaps as reports of distant events accumulate as an overall negative impression of the person's environment.

Research clearly shows that both nature and nurture play important roles in the genesis of psychopathology. (Tsuang, et al. 2004).

Have there been any studies at all investigating the significance of news as part of that environment as a cause of mental disorders?
References
Tsuang, M. T., Bar, J. L., Stone, W. S., &amp; Faraone, S. V. (2004). Gene-environment interactions in mental disorders. World Psychiatry, 3(2), 73.  pmcid: 1414673
There was a talk on this topic at the 2019 Society for Personality and Social Psychology (SPSP) conference. I haven't been able to find a published paper based on the study they presented, but the authors generally concluded that political engagement can be associated with significant mental, emotional, and social health costs.

Reference
Smith, Kevin; Hibbing, John; Hibbing, Matthew (2019). Friends, Relatives, Sanity and Health: The Psychological Costs of Politics. Presented at the annual conference of the Society for Personality and Social Psychology (SPSP). Portland, OR.
Description
Using a nationally representative sample this study investigates the impact of political engagement on the psychological health of the American electorate. Results suggest that among large numbers of Americans politics is linked to stress, depression, various compulsive behaviors and even thoughts of suicide.