How to explain the occurrence of bipolar disorders ? These psychic disturbances are characterized by alternating manic phases with excitement, irritability, effervescence, and phases of depression characterized by great sadness and apathy. Researchers at Mc Lean Hospital (United States) are currently working to understand the risk factors for these disorders, and have particularly studied the link between bipolarity and abnormalities of the circadian cycle (wake / sleep cycle). Their work is published in the journal Biological Psychiatry.
The key role of somatostatin
To do this, they studied the brains of deceased people by analyzing the structure of the neural network and the presence of neurotransmitters, molecules that transmit signals between these cells. The researchers had 15 brains from people with bipolar disorder, 12 brains from people with schizophrenia and 15 control brains. They then observed neuroanatomical changes in bipolar or schizophrenic subjects, particularly in the amygdala, a region of the brain that regulates the response to stress et al’anxiety. This area was indeed very poor in neurons reactive to somatostatin in people with bipolar and schizophrenia. However, at the level of the amygdala, a weak expression of somatostatin can be caused by a disturbance of the circadian cycle. Somatostatin is therefore thought to play a key role in bipolar disorders. More specifically, the peaks of anxiety at the start of the day could be explained by poor regulation of somatostatin in the amygdala during the sleep cycle. “For over 50 years, there has been evidence that something was wrong with the circadian rhythms of people with bipolar disorder, but there was a huge gap between what we understood about the brains of these people and how it altered the cycles. circadians, which contributes to the development of their symptoms“, underlines the doctor Harry Pantazopoulos, principal author of the study, on the site Science Daily.
Towards phototherapy treatments?
However, the authors remain cautious and specify that additional studies are necessary to understand the mechanism of this association between the circadian cycle and bipolar disorders and to know whether it is a correlation or a cause and effect link. Their hope, in the longer term, is to identify this phenomenon sufficiently to find new therapeutic avenues, for example by using the phototherapy to regulate the circadian cycle. Last December, researchers in neuroscience and psychiatry had already shown that genes controlling circadian cycles could be involved in triggering bipolar disorder.
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