Picking up from a Shrink Rap post, I was thinking more about the often asked question of whether we could deal with someone in high office (let's say President, Vice-President, Cabinet Secretary, Senator, or Governor) with a significant history of an Axis I mental disorder. The most likely examples would probably be panic disorder, obsessive-compulsive disorder, depression, or bipolar disorder. As much as I detest stigmatization of mental disorders, I would have to say no, for two reasons: the art of prognosis in psychiatry remains shaky, and psychiatric impairment is often subtle and difficult to demonstrate objectively.
Even if such a candidate for high office had gone years without an episode, or had been stable on medications for a very long time, these kinds of mental disorders are apt to recur without warning. Obviously we know something about psychiatric prognosis: someone who has been hospitalized six times for depression can be expected to have a tougher time of it than someone who has been stable on Prozac for five years. But of the latter person, could I say with any confidence that he or she will likely go the next four or eight years without a major episode (even, of course, considering the major additional stress that elected office would bring)? No.
Most other chronic or recurring disorders are not like this. Hypertension, diabetes, or even heart disease tend to be more predictable over time based on fairly objective criteria. It is the very randomness of mental disorders, at least at our current level of understanding, that makes them so hard to deal with. A medication that has worked for a person for years could stop working tomorrow, and we often don't know why.
The second major concern is that while medical disability from a heart attack or (a la Chief Justice Roberts) a seizure is pretty much evident for all to see, impairment from mental disorders is often open to contentious interpretation. If anxiety, depression, or mania were affecting an elected official's performance, it would likely be subtle, gradual and subjected to partisan debate. This would be very much complicated if the official in question had little insight into the impairment, and chaotic impeachment proceedings might be necessary.
All this could change eventually of course. If or when our understanding of mental disorders progresses to the point where we can more reliably predict and modify their course, then a major mood or anxiety disorder might survive the vetting process. But unfortunately my guess is that we'll see the first female president, and probably even the first gay president, long before we see the first bipolar president.