Studying Monoamine Deficiency

So why should antidepressants be allowed to remain on the market despite the occasional occurrence of devastating side effects? Because they may be the first step to understanding the biological symptoms of depression and using that understanding as treatment. When antidepressants were first placed on the market, their efficacy relied on the monoamine deficiency theory, what I have previously called the chemical imbalance theory. In it's simplest form, it states that a deficiency of certain monoamines (neurotransmitters like dopamine, serotonin, etc.) is correlated with major depression.

This simple theory is rejected by many people who reject antidepressants, such as Peter Breggin, Robert Whittaker and Joanna Moncrieff, writers of popular anti-psychiatry literature. Many have pronounced the theory as incorrect. However, I have found some studies that imply that they may have written their verdict too early. While I don't believe that anyone with knowledge on the subject would claim that monoamine deficiency causes depression, I do not think it is ridiculous to believe that the two may coincide. The first study I read with these implications I mentioned in a previous blog post. It was a study lead by Dr. Jeffery Meyer for the Canadian-Based Centre for Addiction and Mental Health that concluded the enzyme that breaks down serotonin was more prevalent in those who had untreated depression. (For more details, see my earlier blog post "Chemical Imbalance Theory: Fact or Fiction?") After reading a press release about this study, I decided I should examine the source so I found the original article in which the results were published. What I discovered was that the sample size was rather small, a comparison of seventeen depressed patients with seventeen control patients. This is a fact that many skeptics use to dismiss the results of this study and studies like it. However, as I continued my research, I found a follow up study by the same Dr. Jeffrey Meyer that focused even more closely on the effects of SSRIs.

In this second study, twenty-eight control subjects were compared with sixteen subjects suffering from major depression and another eighteen subjects in recovery from major depression. Those with major depression were treated with SSRIs and the activity of the enzyme MAO-A VT, whose activity would decrease the number of monoamines. It was shown that the depressed patients had higher enzyme activity than the healthy patients, and that patients in recovery who had more enzyme activity were more likely to experience recurrence. As the study states, this does not only imply the correlation between monoamine deficiency and depression but it also seems to indicate that continued SSRI treatment, even during remission, is advisable in order to prevent recurrence of the depressive episodes. This is a significant positive outcome towards the demonstration of the usefulness of antidepressants, all of which function by increasing the concentration of monoamines in the brain. Studies like these make me hesitant to dismiss antidepressants and convince me that they can be a productive part of a depression patient's treatment plan.

This is a diagram from the first study posted to better under the mechanisms of monoamine deficiency. Figure A demonstrates the enzyme and monoamine activity in a healthy person. Figure B demonstrates the enzyme and monoamine activity in a major depressive episode. Note the higher concentration of enzyme and the lower concentration of monoamines. Figure C demonstrates what occurs when the monoamine transporter that would normally take monoamines away from the site is low, partially balancing out the excess enzyme. Figure D demonstrates what happens when there is both excess enzyme and a high level of monoamine transporter.

I am not one to rely on one doctor's set of studies, so I will examine the two other relevant studies I found in my next blog post.

Nauert, Rick. "Depression's Chemical Imbalance Explained | Psych Central News." Psych Central.com. Web. 02 Mar. 2012. <http://psychcentral.com/news/2006/11/09/depressions-chemical-imbalance-explained/398.html>.

 Meyer, Jeffrey. "Brain Monoamine Oxidase A Binding in Major Depressive Disorder: Relationship to Selective Serotonin Reuptake Inhibitor Treatment, Recovery, and Recurrence." Archives of General Psychiatry, a Monthly Peer-reviewed Medical Journal Published by AMA. Dec. 2009. Web. 15 Mar. 2012. <http://archpsyc.ama-assn.org/cgi/content/full/66/12/1304>.

 Meyer, Jeffrey. "Elevated Monoamine Oxidase A Levels in the Brain: An Explanation for the Monoamine Imbalance of Major Depression." Archives of General Psychiatry, a Monthly Peer-reviewed Medical Journal Published by AMA. Nov. 2006. Web. 15 Mar. 2012. <http://archpsyc.ama-assn.org/cgi/content/full/63/11/1209>.