This clinical trial is focused on studying the effects of a treatment for residents in nursing homes who have significant depressive symptoms and a type of memory and thinking problem known as neurocognitive disorder. The treatment being tested is called EMONO, which is a combination of two gases, nitrous oxide and oxygen, used as an add-on therapy to conventional antidepressants. The study will compare the effects of EMONO with a placebo, which in this case is Medical Air, a mixture of nitrogen and oxygen.

The purpose of the study is to see if EMONO can help improve depressive symptoms in people who have not responded well to at least one standard antidepressant. Participants will receive the treatment through inhalation, which means breathing in the gas. The study will last for several weeks, during which participants will be monitored for changes in their depressive symptoms and overall well-being. The main focus will be on how symptoms change from the start of the study to four weeks later.

Throughout the study, participants will have regular check-ups to assess their mood and any side effects they might experience. The study aims to provide valuable information on whether EMONO can be a helpful addition to existing treatments for depression in people with neurocognitive disorders. This research could lead to better treatment options for those living with these challenging conditions.