Depression and its Treatments

I deeply apologize.  I've let this past week get the best of me as I have been extremely, ridiculously busy.  My apologies for not updating on the regular basis as I have in the past.  But I really will try to keep to a more consistent schedule from here on out.  And to get started, let's talk about depression!

Ok, so maybe I said that with a bit too much enthusiasm.  It's just the idea of something so hard to pin down- like emotions- coming from a neurological basis fascinates me.  Surely we all want to believe our moods aren't caused by the whims of our neurotransmitters and synapses.

This Van Gogh painting is the first thing to
pop up when you search for "depression"
via google.

But there is plenty of strong evidence that explains depression (or at least most of its varieties) stem from a lack of three neurotransmitters.  Serotonin, norepinephrine, and dopamine are the main ingredients lacking in a depressed individual.  And most of our modern treatments try to enhance these neurochemicals in some way.

MAO Inhibitors were part of the first generation of anti-depressant drugs.  They blocked an enzyme which breaks down monoamines.  All three of the transmitters mentioned above fall into this category so the MAO inhibitors basically kept them circulating in a persons system for a longer period of time.

Then came the tricyclics.  Their primary focus was preventing reuptake of serotonin and norepinephrine by the surrounding cells.  Once again, this keeps the transmitters in the brain for a longer period of time so they can be more effective.  And tricyclics had less side effects than MAO inhibitors.

The newest of the drug types is SSRI (selective serotonin reuptake inhibitors).  They act in much the same way as tricyclics except they have even less damaging side effects because they are so much more specific.

This is an image of an actual patient who
underwent the deep brain stimulation surgery.

But even with all the pharmacological changes, the most potent treatment is so radical that it has only been tried on a few human patients.  It's called deep brain stimulation.  Basically, a neurologist places electrodes deep into the brain tissue of their patients and switches them on.  Some about the current of these electrodes affects an inhibitory pathway which quiets the subgenal cingulate part of the brain.  Patients report feeloing immediately relief with none of the lag which drugs possess.  They also feel the immediate change if you were to turn off their electrodes- whether they were aware you were doing so or not.  So this isn't just the placebo effect at work.  I'd be curious to see where this research progresses in the future.  Aren't you?

Saving the Brain

I want to revisit the topic of neurogenesis (the growth of new neuron cells) because while it may be that adult brains can form new neurons, they can't do so to the degree found with brains experiencing the critical period.  The critical period occurs when between late embryonic stages and early life.  This is when massive amounts of new neurons are created and preliminary synapses are growing towards as many targets as possible.

The power of a single synapse is weak, but together in a
circuit their power is incredible. 

After the critical period, there is a massive reduction in the number of connections between neurons.  The ones that remain are typically efficient enough to handle all the mental processes but the ability to "rewire" after this period is severely reduced.

However, some recent research is leading us to believe that there may be a way to reopen the critical period  and at least partially rewire our brains.  In fact, some antidepressants seem to be doing just that.  There's now evidence that anti-depressants like fluoxetine work by increasing BDNF (brain derived neurotrophic factor) which is hallmark of the critical period.  Fluoxetine requires chronic usage to get these effects but perhaps the antidepressant allows for the creation of new synapses and connections.  Maybe the rewiring is changing how information is processed in the emotional centers of the brain, thus relieving the depression of the patient.

A pill that changes how your brain is wired-
scary or amazing?

There's still plenty of research and trails we have yet to undergo before we understand all the mechanisms.  But this offers hope that neuroplasticity can be raised to the high level of malleability found during the critical period.