Jonah Lehrer, at
href="http://scienceblogs.com/cortex/2006/10/depression_induces_bone_loss_1.php">The
Frontal Cortex,
points out a recent PNAS article (published online ahead of print) that
indicates an unexpected finding. Using a mouse model or
depression, they find that the risk of osteoporosis is increased.
Furthermore, they find that treatment with an antidepressant
reduces the risk.
href="http://www.pnas.org/cgi/content/abstract/0604234103v1">Depression
induces bone loss through stimulation of the sympathetic nervous system
Raz Yirmiya, Inbal Goshen, Alon Bajayo, Tirzah Kreisel, Sharon Feldman,
Joseph Tam, Victoria Trembovler, Valér Csernus, Esther
Shohami,
and Itai Bab
Major depression is associated with low bone mass and increased
incidence of osteoporotic fractures. However, causality between
depression and bone loss has not been established. Here, we show that
mice subjected to chronic mild stress (CMS), an established model of
depression in rodents, display behavioral depression accompanied by
impaired bone mass and structure, as portrayed by decreases in
trabecular bone volume density, trabecular number, and trabecular
connectivity density assessed in the distal femoral metaphysis and L3
vertebral body. Bone remodeling analysis revealed that the CMS-induced
skeletal deficiency is accompanied by restrained bone formation
resulting from reduced osteoblast number. Antidepressant therapy, which
prevents the behavioral responses to CMS, completely inhibits the
decrease in bone formation and markedly attenuates the CMS-induced bone
loss. The depression-triggered bone loss is associated with a
substantial increase in bone norepinephrine levels and can be blocked
by the {beta}-adrenergic antagonist propranolol, suggesting that the
sympathetic nervous system mediates the skeletal effects of
stress-induced depression. These results define a linkage among
depression, excessive adrenergic activity, and reduced bone formation,
thus demonstrating an interaction among behavioral responses, the
brain, and the skeleton, which leads to impaired bone structure.
Together with the common occurrence of depression and bone loss in the
aging population, the present data implicate depression as a potential
major risk factor for osteoporosis and the associated increase in
fracture incidence.
Of course, I would be cautious about inferring that this can be used to
draw any conclusions about humans, either in terms of pathophysiology,
or treatment. A quick
href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed">Medline
search for "osteoporosis depression" and "osteoporosis antidepressant"
will turn up some studies in humans that show a correlation, and some
that do not.
Jonah comments, "So much for mind-body duality." Indeed.
The body does not know that it is supposed to act like a
collection of independent systems (nervous system, skeletal system,
etc.) It has this annoying tendency to act as a single
unified
system, not a bunch of parts. This makes it more difficult to
understand, although it probably works better that way.
One thing that is illustrated by this type of article is that when you
weight the risks and benefits of any kind of medical treatment, you
want to consider the risks and benefits to the body as a whole, not
just the organ system you are treating. And you need to
consider
the fact that risks and benefits can affect systems other than the one
you are targeting. And you need to consider the fact that
there
are risks and benefits to treatment, but also risks and benefits to not
treating.
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Like so many of these things, there's a connecting of the dots that is plausible, yet there can be other dot-connecting schemes just as valid.
It may be that the benefit is more of an epiphenomenon rather than some pure effect of the medicine.
I'm sure you too have some issues with animal models of mental illness in general. Just what is the behavior of a rat that denotes depression? Is there a DSM-IV for rats? Many times these are sort of a circular logic -- the behavior kinda-sorta looks like the rats are depressed, it's "helped" by antidepressants, so it must be depression.
And we are also seeing these leaps to neurochemistry to explain the "mechanism", as if we can alter one, just one, neurotransmitter in the brain and have no effect on any other.
Hmmm... calcium is calming. Maybe people losing bone mass have low blood calcium and that causes depression. Or perhaps depression leads to less activity leads to bone loss.
For the past 6 months I was having heart palpitations (and I do have MVP), headaches (which I have never been prone to), anxiety attacks, short term memory loss, changes in vision, a heavy foggy feeling when waking, sleeplessness, periodic high blood pressure (which is usually low), and a drastic switch from hypo to hyper thyroidism that was followed by lethargy. Bone mass loss then also can be a concern. I thought I was losing it. After seeing the Endocrynologist, I was prescribed Propranolol to ease some of the symptoms until all of the appropriate tests were run and a running glucose meter check was accomplished. There was immediate relief. I was amazed. It does not replace the need to get the tests done and follow-up with the Dr., but I have always been active and it sure is great to feel more myself again.