Every paper I've seen on the subject has pretty much monotonic improvement in reported mental health outcomes almost all the way to the right, and if there's any non-monotonicity, it's insufficient to come even close to the reported negative mental health outcomes on the far left. This is not a formal scientific paper, but the SSC survey has the benefit of tighter granularity and more heterodoxy than most sources. https://mobile.twitter.com/phl43/status/1227338353101672450
Low granularity research from gallup: https://news.gallup.com/poll/102943/republicans-report-much-...