extreme moodsI can think of no better example of the phenomenon of state-dependent learning than the mother of two who came into my office one early Fall morning experiencing extremely intense emotions (racing thoughts, and panic attacks) who had had a very similar mood experience 10 years ago when she gave birth to her first child.

As the result of the change in her mood she found herself suddenly re-immersed in experiencing the pain and fear and anxiety that accompanied that event.  The experience of remembering was so intense that she actually felt, for a brief while, as though she might be pregnant again.  She noticed that she was walking in the way that women who are very pregnant will walk.  She re-experienced the pain of delivery and the pain and terror that accompanied realizing that the spinal anesthesia was not working.  All of these experiences of childbirth, usually distant from most women’s memory, started flooding in on her because her mood at the moment was very similar to the mood she experienced at that time.

We have talked elsewhere about why this happens.  About how memory is intrinsically organized by emotion because how it gets stored in the frontal cortex depends on the activity of the hippocampus, which essentially acts as the card catalogue, or index, for memories.  And because the hippocampus is in the limbic, or emotional brain, memories are stored and organized according to your mood at the moment you store the memory.

When we’re in a certain mood, particularly when that mood is very powerful, we find ourselves vividly remembering usually distant memories of events that took place when we were in that very same mood before.

And, the everyday significance of that for me, as a psychiatrist working with people who have mood ups and downs, is that people who are depressed will often not remember being hypomanic. They will report that they have always been depressed. And this is not caused by a conscious process of denial, it is just that the memory of those other states is distant and hard to bring to mind.

Which is part of why it is hard to distinguish between bipolar depression (where there are states of depression but also energized states in between) and unipolar depression (where what changes is the severity of the depression, but there are no energized states.