Sunday, February 3, 2013

Circadian Rhythms and Bipolar Disorder: Scientific Update

It has been some time since I wrote a post on scientific research, which was to be the focus of this blog but I expanded it into many things bipolar while staying on the science side. This post is one way to indulge my hypergraphia.

In selecting articles to review for this blogpost, I first find articles I understand as many neuroscience articles can be highly technical. Second, I find articles that have some practical utility to people living with bipolar disorder. So I tend to avoid articles that are related to mice or other animals. 

The first article is about the circadian rhythms. According to the National Institute of General Medical Sciences (NIGMS), which is a part of the National Institutes of Health (NIH), circadian rhythms are the physical, mental and behavioural patterns that closely follow a 24 hour cycle. These patterns are found in most living things including animals, plants and even microbes. Chronobiology is the study of circadian rhythms. Produced by natural factors in the body, circadian rhythms are also affected by factors in the environment with light being the most important as it controls the genetic switches that influence these patterns. Circadian rhythms influence many bodily functions such as body temperature, hormone releases and sleep/wake patterns. 


Circadian rhythm characteristics in mood disorders: Comparison among bipolar I disorderbipolar II disorder and recurrent major depressive disorderChung, JK, Lee, KY, Kim, SH et al. (012) Clinical Psychopharmacology and Neuroscience, Vol 10(2), Aug, 2012. pp. 110-116.

Summary of Findings
This Korea-based study used factor analysis to study data on how people experience the rhythms of day and night and found that people with mood disorders were more likely to be evening types than people with no mood disorders. Those with bipolar disorder I were more likely to have evening tiredness than those with bipolar disorder II. Those with bipolar I scored higher for morning alertness than people with recurrent major depressive disorder (RMDD).



The second article is highly technical and the practical implications are not as explicit but the findings are worth a mention because they reinforce the link between abnormal circadian rhythm patterns and bipolar disorder.

A survey of genetic studies supports association of circadian clock genes with bipolar disorder spectrum illnesses and lithium response. McCarthy, MJ, Nievergelt, CM, Kelsoe, JR, & Welsh, DK. (2012), PLoS ONE, 7(2) 

Summary of Findings
This study acknowledges the relationship between abnormal circadian rhythms and bipolar spectrum disorders and that this has inspired the search for genetic sources for this abnormality. However, to date there have been no significant findings from this research that would link genes to these abnormalities. The researchers list 3 factors that could be a reason for this lack of significant findings: 1. complex traits usually involve more than one gene; 2. circadian rhythms may be more complicated than they first appeared; and, 3. genetic risk for bipolar disorder could be spread among many illnesses. Without going into technical detail, the major finding was that their analysis revealed previously unrecognized links between bipolar disorder and circadian rhythms.

Circadian rhythms and bipolar disorder. Murray, G. (2010). Bipolar Disorders, 12(5), 459-472

Summary of Findings

This accessible article is a review of existing literature on the relationship between abnormal circadian rhythms and bipolar disorder. It does not present anything particularly new but does reinforce what is already known.

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