Got it and thanks for clarifying. I also amended my last comment since I had a bit of extra time to read the study more thoroughly. I’d be quite interested to see which way the causation goes. Although I suspect that hyperstable arousal may be a symptom of depression rather than a cause of depression, I have heard that the intense adrenaline rush of skydiving may alleviate depression for some people. To me this suggests there may be a way to break out of that hyperstable arousal state by intentionally reaching a state of extremely high arousal, perhaps ending a bout of depression early.