Stress and Depression
If I had to define a major depression in a single sentence, I would describe it as a "genetic/neurochemical disorder requiring a strong environmental trigger whose characteristic manifestation is an inability to appreciate sunsets." (Location 4471)
“Hedonism is the pursuit of pleasure, anhedonia is the inability to feel pleasure” (also often called dysphoria). (Location 4478)
⇒ Dopamine
Another frequent feature is psychomotor retardation: the person moves and speaks slowly. Everything requires tremendous effort. She finds the act of merely arranging a doctor’s appointment exhausting. (Location 4515)
Profoundly depressed people rarely attempt suicide. It’s not until they begin to feel a bit better. If the psychomotor aspects make it too much for this person to get out of bed, they sure aren’t going to find the considerable energy needed to kill themselves. (Location 4519)
While depressives don’t necessarily have trouble falling asleep, they have the problem of “early morning wakening” — spending months on end sleepless and exhausted from three-thirty or so each morning. Not only is sleep shortened but the “architecture” of sleep is disturbed. (Location 4528)
⇒ Sleep and Stress
The pure process of storing and retrieving memories via the Hippocampus is often impaired. (Location 4540)
Seasonal affective disorder (SAD): the rhythm is annual — sufferers get depressed during the winter. A class of retinal cells responds to light intensity and sends information directly into the Limbic System, the emotional part of the brain. (Location 4563)
Why it is likely that there is something wrong with Norepinephrine, Serotonin, or dopamine in depression? The best evidence is that most of the drugs that lessen depression increase the amount of signaling by these neurotransmitters. (Location 4595)
⇒ Hormones of the Stress-Response
Dopamine signals the anticipation of reward more than it signals reward itself. (Location 4675)
People with chronic depressions are those whose cortex habitually whispers sad thoughts to the rest of the brain. The anterior cingulate cortex (ACC) — it turns out to have all the characteristics of a brain region you’d want to take offline in a major depression. If you electrically stimulate the ACC in people, they feel a shapeless sense of fear and foreboding. Moreover, neurons in the ACC respond to pain — but the response isn’t really about the pain; it more concerns feelings about the pain. The more left out the person feels, the more intensely the ACC activates. (Location 4704)
The far more common feature of depression is one of an overactive stress-response — somewhat of an overly activated sympathetic nervous system and, even more dramatically, elevated levels of Glucocorticoids. Depressed people, sitting on the edge of their beds without the energy to get up, are actually vigilant and aroused, with a hormonal profile to match—but the battle is inside them. (Location 4850)
The excessive secretion of glucocorticoids in depression is due to feedback resistance — the brain is less effective than it should be at shutting down glucocorticoid secretion. (Location 4857)
⇒ Stress and Aging
Sustained stress will deplete Dopamine from the “pleasure” pathways, and Norepinephrine from the alerting locus ceruleus part of the brain. Moreover, stress alters all sorts of aspects of the synthesis, release, efficacy, and breakdown of serotonin. (Location 4868)
Chronic depression has also been associated in some studies with decreased volume in the Frontal Cortex. (Location 4883)
Genes are rarely about inevitability, especially when it comes to humans, the brain, or behavior. They’re about vulnerability, propensities, tendencies. Genes increase the risk of depression only in certain environments — only in stressful environments. (Location 4837)
People who are prone to depression tend to experience stressors at a higher than expected rate. Stressors built around lack of social support can create a vicious cycle: interpreting ambiguous social interactions as signs of rejection can increase the chances of winding up socially isolated, thereby confirming the sense of rejection. (Location 4802)
see also
Tags: neuroscience science
Superlink: 050 🧠Neuroscience 051 ☣Neurobiology
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Erstellt: 05-04-26 10:00