A large number of people who develop mood disorders such as bipolar (BD) and major depression (MDD) also have at least one family member with BD. There is a strong genetic link with these issues, and immediate relatives of individuals with BD are ten times more likely to develop BD and three times more likely to develop MDD than individuals with no family history of mood issues. Understanding the earliest signs and additional risks for MDD and BD could help identify those most at risk and enable clinicians to initiate treatment at an earlier time in order to improve the overall outcome. The prodromal symptoms of MDD and BD have been explored at length, but clinical markers for BD have not. Therefore, Heather C. Whalley of the Division of Psychiatry at the University of Edinburgh in the U.K. recently conducted study comparing neurological images of 98 high risk individuals from families with BD histories (HR) to those of 58 control participants with no family history of BD.
Whalley found that even though none of the participants had any symptoms of BD or MDD, 20 of the HR participants had increased insula cortex activation compared to the control participants and the remaining HR participants. Upon follow-up two years later, these same 20 participants met the clinical criteria for MDD. The insula is a region of the brain associated with emotional regulation, reaction inhibition, and subjective emotional response. In the 20 HR participants who later developed MDD, the insula did not disengage as the participants completed tasks during the experiment. But the HR participants who did not develop MDD and the control subjects all had increasing levels of disengagement as the experiment tasks increased in difficulty. These results show that even if symptoms are not present, neurological markers exist that can potentially identify high-risk individuals vulnerable to MDD. Whalley notes that although none of the participants developed BD during her study period, some people experience depressive symptoms years before the onset of BD. She hopes that this research will increase early diagnoses in those most vulnerable to future mood issues. She added, “These findings advance our understanding of the biological processes involved in the development of mood disorders and provide a potential biomarker that could be tested for clinical utility in future studies.”
Whalley, H.C., Sussmann, J.E., Romaniuk, L., Stewart, T., Papmeyer, M., et al. (2013). Prediction of depression in individuals at high familial risk of mood disorders using functional magnetic resonance imaging. PLoS ONE 8(3): e57357. doi:10.1371/journal.pone.0057357
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