T
Thorolfr
Guest
The brain is a physical organ of the body just like the heart. It is made up of cells called neurons which communicate with each other using chemicals called neurotransmitters. As Kandel notes in his book (pp. 64-65):My sister just recently had her mitral valve replaced = physical cause. Head trauma (injury) resulting from a car accident resulting in cognitive impairment = physical cause.
Depression is due to a chemical imbalance within the brain, not an abnormality of the brain itself, but how it functions - you’re correct there in it’s malfunction - not physical injury/deformity etc.
Based on recent studies, there is little doubt that psychiatric disorders like depression are indeed due in part to abnormalities in certain parts of the brain itself, in cortical area 25, the right anterior insula and the gyrus. All those brain areas function abnormally in people who suffer from depression and other mood disorders. And part of the reason that these areas function abnormally in people with depression or bipolar disorder is because of their genes. As Kandel says:Until quite recently psychiatric disorders were notoriously difficult to trace to particular regions of the brain. But today’s brain-imaging technology, specifically PET and functional MRI, have enabled scientists to identify at least some of the neural circuits responsible for depression…Helen Mayberg, a neurologist now at Emory University, found that the neural circuit of depression has several nodes, two of which are particularly critical: cortical area 25 (the subcallosal cingulate cortex), and the right anterior insula. Area 25 is a region where thought, motor control, and drive come together. It is also rich in neurons that produce serotonin transporters - proteins that remove serotonin from the synapse. This is important because serotonin is a modulatory neurotransmitter released by a class of nerve cells to help regulate mood. Modulatory transmitters don’t simply tansmit an impulse from one cell to the next, but “tune” whole circuits or regions. Serotonin transmitters are particularly active in depressed people and are partially responsible for lowering the concentration of serotonin in area 25…Another brain structure that is consistently implicated in both major depressive and bipolar disorders is the gyrus, or raised fold, of the anterior cingulate cortex…Both regions function abnormally in people with mood disorders, which accounts for their varied emotional, cognitive, and behavioral symptoms. The region concerned with emotion is consistently overactive during major depressive episodes and the depressive phase of bipolar disorder.
And genes are also partially responsible for some people being more likely than others to suffer from heart disease or other medical illnesses.For the most part, our genes determine whether we are likely to develop a mood disorder. Studies of identical twins who are reared apart - the best way to separate nature from nurture - indicate that if one twin has bipolar disorder, the other twin has a 70 percent chance of developing it.
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