Q:  If a person with bi-polar probs, misses  medication for a length of time, will this cause brain damage? and irreversable effects?

Dear Mr. T' --
There is some very limited evidence that having symptoms of severe depression, or symptoms of "psychosis" (losing contact with reality) -- and I think by extension probably symptoms of bipolar mania, although there is no direct evidence of that to my knowledge -- can cause bad changes in the brain.  However, the good news is that those changes, for depression at least, appear to be reversible.  Lithium has been shown in one small study to be able to reverse it, and in my experience with patients I've seen memory improvements (the memory system, the "hippocampus", is one of the two places the changes are seen; the other is frontal lobes; here's a Brain Tour if you want a map) even without lithium, just when the symptoms are controlled, with any of several medications.  

As for psychosis, I don't watch that literature as closely so I'm not sure if that is thought to be reversible. A quick search seems to confirm that psychosis is indeed thought to be associated with "brain damage", but only in a rather vague way and this is not as well documented as what happens in depression.  No data I found on reversibility, probably because we don't understand the mechanism as well as for depression. 

However, the main point here is that yes, it's probably true that there are brain changes with these illnesses.  How long can one miss doses?  A few days? a week?  What matters is the risk of bringing on another episode, because in our current models for this,  each episode is associated with some risk for further brain changes at some level.  Some people can miss quite a few doses, some people show relapse symptoms if they miss just a few days in a row. 

Dr. Phelps

Published June, 2003