Is the dark really making me sad? | Ars Technicathe leading theory is the ‘phase-shift hypothesis’: the idea that shortened days cause the timing of our circadian rhythms to fall out of sync with the actual time of day, because of a delay in the release of melatonin. Levels of this hormone usually rise at night in response to darkness, helping us to feel sleepy, and are suppressed by the bright light of morning. “If someone’s biological clock is running slow and that melatonin rhythm hasn’t fallen, then their clock is telling them to keep on sleeping even though their alarm may be going off and life is demanding that they wake up,” says Kelly Rohan, a professor of psychology at the University of Vermont. Precisely why this should trigger feelings of depression is still unclear. One idea is that this tiredness could then have unhealthy knock-on effects. If you’re having negative thoughts about how tired you are, this could trigger a sad mood, loss of interest in food, and other symptoms that could cascade on top of that. However, recent insights into how birds and small mammals respond to changes in day length have prompted an alternative explanation. According to Daniel Kripke, an emeritus professor of psychiatry at the University of California, San Diego, when melatonin strikes a region of the brain called the hypothalamus, this alters the synthesis of another hormone—active thyroid hormone—that regulates all sorts of behaviours and bodily processes. When dawn comes later in the winter, the end of melatonin secretion drifts later, says Kripke. From animal studies, it appears that high melatonin levels just after the time an animal wakes up strongly suppress the making of active thyroid hormone—and lowering thyroid levels in the brain can cause changes in mood, appetite, and energy. For instance, thyroid hormone is known to influence serotonin, a neurotransmitter that regulates mood. Several studies have shown that levels of brain serotonin in humans are at their lowest in the winter and highest in the summer. In 2016, scientists in Canada discovered that people with severe SAD show greater seasonal changes in a protein that terminates the action of serotonin than others with no or less severe symptoms, suggesting that the condition and the neurotransmitter are linked.
Light boosts serotoninExposure to bright light is a second possible approach to increasing serotonin without drugs. Bright light is, of course, a standard treatment for seasonal depression, but a few studies also suggest that it is an effective treatment for nonseasonal depression38 and also reduces depressed mood in women with premenstrual dysphoric disorder39 and in pregnant women suffering from depression.40 The evidence relating these effects to serotonin is indirect. In human postmortem brain, serotonin levels are higher in those who died in summer than in those who died in winter.41 A similar conclusion came from a study on healthy volunteers, in which serotonin synthesis was assessed by measurements of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the venous outflow from the brain.42 There was also a positive correlation between serotonin synthesis and the hours of sunlight on the day the measurements were made, independent of season. In rats, serotonin is highest during the light part of the light–dark cycle, and this state is driven by the photic cycle rather than the circadian rhythm.43,44 The existence of a retinoraphe tract may help explain why, in experimental animals, neuronal firing rates, c-fos expression and the serotonin content in the raphe nuclei are responsive to retinal light exposure.44–48 In humans, there is certainly an interaction between bright light and the serotonin system. The mood-lowering effect of acute tryptophan depletion in healthy women is completely blocked by carrying out the study in bright light (3000 lux) instead of dim light.49
Tanning dependence linked to other addictive behaviors, new study finds -- ScienceDailyThe connections between tanning dependence and other disorders revealed by the study represent an opportunity for clinicians to address those related conditions. "People who are tanning dependent could also be assessed for SAD," said Cartmel. "There are ways of addressing SAD other than indoor tanning. Regarding the alcohol dependence association, it may be possible that addressing that behavior could help address tanning dependence." The underlying mechanisms for the addiction to UV light are not yet fully understood. According to other studies, "The biological rationale for tanning dependence is that exposure to UV light results in both melanin, and endorphin production," said Cartmel. She also added that there was another interesting preliminary finding: those with tanning dependence were five times more likely to exhibit "exercise addiction." She said it is too early, however, to determine the implication. "Exercise addiction" itself has really not been well researched," she said. "One hypothesis behind the finding is that people who exercise excessively do so because they are very aware of their appearance, and they also feel that being tanned improves their appearance. Or it may be that we will eventually find out that these individuals have more of an addictive or risk-taking personality type. If you have one type of dependence, you may be more likely to have another addiction," Cartmel said.
The mix-up happened when MIT combined two separate lists for an electronic mailing about financial aid. At the bottom was a footer that said “You are on this list because you are admitted to MIT,” according to Peterson. By merging the lists in a program called MailChimp, admissions officers mistakenly imported the footer from a list of students accepted under early admissions. The note at the bottom was supposed to say “You are receiving this e-mail because you applied to MIT and we sometimes have to tell you things about stuff,” according to the blog.