Recognize the Interoception Collapse Before It Becomes Permanent
Most people watching for bipolar disorder look for the obvious behavioral signals: the spending sprees, the sleeplessness, the pressured speech. Huberman points to a deeper and more consequential change that happens underneath all of that. Over the second and third decade of having bipolar disorder, the neural circuits responsible for interoception, the brain's ability to sense what is happening inside the body, progressively atrophy. Interoception is what tells you that you have not slept in five days, that you are speaking too fast, that you have not eaten. In someone with advancing bipolar disorder, that signal degrades and eventually disappears. This is not a psychological failure of self-awareness. It is a structural change in the brain. The mechanism appears to be excitotoxicity. When certain neural circuits are hyperactive for extended periods, the calcium and glutamate released by that activity begin to kill the very neurons doing the work. Lithium's neuroprotective effect, its ability to shield neurons from this kind of stress-driven death, is now understood to be one of its core mechanisms of action. The earlier treatment begins, the more of that interoceptive circuitry can be preserved. Waiting is not neutral. Every untreated manic episode carries a structural cost.