US researchers have found a correlation between levels of the brain chemical neuropeptide Y (NPY) and an individual's emotional wellbeing. Mutations in the NPY gene, leading to decreased levels of the molecule, correlated with a decreased ability to deal with stressful situations and an increased susceptibility to depression.
'This is what we mean when we talk about personalised medicine. These are genetic features that can be measured in any person. We hope they can guide us toward assessing an individual's risk for developing depression and anxiety', said Dr Brian Mickey of the University of Michigan who led the study.
NPY is a chemical transmitter found in the brain, as well as in the bloodstream and spinal fluid. Different mutations within the NPY gene are known to increase or decrease NPY levels in the body. Researchers subjected 181 individuals with these various mutations to two different stress tests.
In the first test, participants underwent functional magnetic resonance imaging (fMRI) to monitor their brain activity while being shown different words. Negative words, such as murder, resulted in greater activity in regions of the brain associated with depression in subjects with low NPY levels compared to those with higher NPY levels.
In a second test, participants were asked to describe their emotions before and after a painful, but harmless, treatment was applied. An injection of saline solution into the jaw resulted in moderate levels of pain. The pain elicited was standardised for each individual, such that they ranked it as a 4 out of 10. People with low NPY levels experienced more negative emotions both before and after the treatment compared to those with higher NPY levels.
In addition to these tests, NPY levels were analysed in people diagnosed with major depressive disorder (MDD) and compared to a control group. A higher incidence of NPY mutations causing low NPY levels was found in the MDD group.
These findings may therefore shed light on the genetic predisposition towards depression and anxiety. Professor Jon-Kar Zubiet who was also involved in the study, said: 'We're not just associating a particular gene with a particular illness. We're expanding the understanding of the physiology of depression'.
This study was published in the Archives of General Psychiatry.
Sources and References
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Born miserable — some people genetically programmed to be negative
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Pessimism is in the genes
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Depression: Here’s a gene that may make some folks more susceptible
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Emotion processing, major depression, and functional genetic variation of neuropeptide Y
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New link between genes and stress response, depression: Neuropeptide Y
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