journals.sagepub.com/doi/…/2167702620921341 - the bigger takeaway from this one is that trigger warnings reinforce trauma as a central part of the traumatized individuals identity but they did find some incidence of drawback/harm
There are others, this is just what grabbed from 30 seconds on google scholar. Its been a bit since I’ve done more serious lit review and it’s not like I keep a directory of papers I’ve read
The issue is the culture surrounding trigger warnings. Let’s be real here, people looking for trigger warnings are generally (perhaps overwhelmingly) not looking for material to help with their exposure therapy. They are looking for a “warning” to help them screen material to avoid. The issue is that this creates an unrealistic expectation that is incompatible with the real world. You can avoid suicide, sexual assault, eating disorders, or whatever in your media (maybe) but real life won’t sanitize itself or warn you. You will encounter these topics, whether through the news, careless speech from friends, or even intrusive thoughts of your own. Research continues to show that avoidance of upsetting topics can worsen anxiety and ptsd symptoms
To your final point the idea of it helping to create a choice isn’t even as clear cut as you describe
journals.sagepub.com/doi/…/21677026221097618 content warnings actually increase the likelihood someone will view problematic content. This point is further reinforced by similar findings in the meta linked above
So you have a system that ultimately makes creators feel like they’re doing something noble, that is likely at best useless and potentially harmful. Said system increases the likelihood that a person will view the problematic content but also enables the reality that a person will simply avoid the things that provoke their anxiety which again is more strongly established as harmful