There’s evidence that trigger warnings actually worsen anxiety and are counterproductive
The way to treat anxiety is to face the source of anxiety to try and change your relationship and reaction. The best way to do this is via controlled access that exposes one to the trigger gradually in a context that has no risk of harm (eg a media depiction, discussing the concept, building up to discussing the source of trauma that led to the phobic response if applicable)
Trigger warnings enable active avoidance. This sensitizes one to the aversive stimuli and makes the phobic response stronger. As a result when one encounters the stimulus (eg a friend, family, celebrity etc commits suicide, suffers an eating disorder, etc) your resilience to the trigger is now even lower and the response is more likely to be more significant than it was before.
That said education on access to resources like 988 or other warm lines can lower suicide rates, maybe. Research is more mixed here because it’s difficult to prove causation