Of Bipolar Disorder, The Hippocampus, and The Return of the Exercise Fiend

My mother highly valued intelligence, and her way of putting down someone she saw as sub-par in the smarts department was saying, “He’s no brain surgeon, I’ll tell you that.” But I, literally, am no brain surgeon, so to discuss this latest research I have to do one of those “let’s start at the very beginning” Julie Andrews routines.

So, you’ve got a brain. So far, so good. And the brain has what is known as a limbic system. The limbic system is a set of structures that make up the inside of the cortex, which, in turn, is the tissue that is just outside [I know this is getting to be like “The House That Jack Built,” but hang in there for just a few more moments] the cerebrum, which basically heads up your central nervous system. The limbic system is crucial in the experience of emotion–and memory, too, by the way.

Ok, one of those structures in the limbic system [and this is where I really wanted to get to] is known as the hippocampus.

Essentially, it’s part of the brain’s mood center. And it’s pretty sensitive, it turns out. In a research study examining the effects of chronic stress on rats, Fred Helmstetter of the University of Wisconsin found that the rats’ hippocampal volumes shrank in response to chronic stress.

Included among chronically stressful conditions is the stress of mental illness, or, for our purposes, bipolar episodes.

For years, brain autopsies on people with bipolar illness have showed decreased density in the hippocampus. A freshly published study entitled “Hippocampal Interneurons in Bipolar Disorder,” in the 2011 volume of the Archives of General Psychiatry, compared brains of those with bipolar disorder to those of healthy control subjects.  The abstract results are too wonderfully arcane to deprive you of, so here goes: “the bipolar disorder group showed reduced volume of the nonpyramidal cell layers, reduced somal volume in cornu ammonis sector 2/3, reduced number of somatostatin- and parvalbumin-positive neurons, and reduced messenger RNA levels for somatostatin, parvalbumin, and glutamic acid decarboxylase 1. ” Got it?

What they’re really saying is that the hippocampus is smaller in those who suffer from bipolar disorder.

Despite our rather disheartening knowledge that there is brain atrophy in the bipolar nervous system, there is cause for hope. Because scientists have discovered something remarkable.

Whereas for years it was considered a given that primates were born with a certain number of brain cells, and, apparently, you spent the rest of your life finding ways to lose them, recently scientists have found that neurogenesis [that’s just the process of the brain creating new neurons; it’s nothing to follow compared to all that brain mapping stuff] actually can occur in the hippocampus. That’s right–you can grow new gray matter–if you just know the right tricks.

In “Lithium Builds Gray Matter in Bipolar Brains, Study Shows,” researchers discovered that taking lithium increased volume in the paralimbic regions of the brain, and it has since been demonstrated that consistent treatment with adequate doses of antidepressants increases hippocampal volume, as well.

And, medication aside, we now get to return to one of my favorite topics, which is- in case you’ve forgotten from previous posts–exercise. Just to be clear–I firmly believe that bipolar disorder needs to be treated with a strict medicine regime, rigorously adhered to. I’m not a proponent of going all-natural or organic or touchy-feely, with such a serious illness.

However, in addition to whatever medicine your doctor has prescribed, exercise also holds much promise for not just slowing the shrinkage of the hippocampus cells-but actually reversing the process.

Numerous studies have found that 30 minutes of aerobic exercise three times a week will slow hippocampus volume loss in the elderly, thus working against age-related memory loss. A research study published in the Proceedings of the National Academy of Science entitled “Exercise Training Increases Size of Hippocampus and Improves Memory” found that the exercise impacted hippocampal volume so positively that it was the equivalent or reversing age-related volume loss by 1-2 years.

Under our constant stress theory of volume loss, it should be no surprise that schizophrenia is also, like bipolar disorder, associated with hippocampal shrinkage. Yet in a study of control-sample healthy men and men with schizophrenia entitled “Hippocampal Plasticity in Response to Exercise in Schizophrenia” in the February 2010 issue of the Archives of General Psychiatry, authors Frank-Gerald Pajonk et al found that cycling for 30 minutes 3 times per week increased hippocampal volume–for both groups, even the schizophrenics [and see the link there, “Major Brain Similarities Found in Bipolar Disorder and Schizophrenia.”]

I may be no brain surgeon, but I can understand from the research that exercise will slow and even reverse illness-associated loss of brain volume–and, brain surgeon or no, I get that that’s a pretty good thing.



–Possible causes of, new paths of research, stress and hippocampus shrinkage in bipolar disorder–and what new tools do we have in our arsenal to treat this disorder? See “Tracking down the Footprints of Bipolar Disorder” at http://www.csa.com/discoveryguides/bipolar/overview.php.