The Impact of AMPA Receptor Blockade on Ketamine's Anti-Suicidal Effects

This study is investigating whether blocking a specific brain receptor (the AMPA receptor) affects how well ketamine reduces suicidal thoughts in people with treatment-resistant depression. Ketamine is a medication that can rapidly reduce suicidal thoughts, but researchers don't fully understand why. This study aims to find out. **You may be eligible if...** - You are 18 or older with a current diagnosis of major depression, PTSD, or bipolar disorder - You have significant depressive symptoms and current suicidal thoughts - Your depression has not responded to at least one antidepressant medication - You are currently receiving mental health treatment - Your current medications have been stable for at least 4 weeks **You may NOT be eligible if...** - You have a history of psychosis, schizophrenia, or certain other serious psychiatric conditions - You have moderate-to-severe substance use disorder - You have serious, unstable heart or liver problems - You are pregnant or breastfeeding - You are not currently engaged with a mental health provider Talk to your doctor to see if this trial is right for you.