With autumn upon us, darker days and moods may be ahead. Here’s what to do about it.

The coronavirus shadows that crept across the region an equinox ago have persisted, and now we are experiencing something that likely ranks beneath the bottom of our list of needs — longer shadows.

On yet another October-like morning, in which the temperature dropped to 33 in Blue Bell, Montgomery County. and set a record in Wilmington, the autumnal equinox arrived at 9:30 a.m. Tuesday, when for an existential instant the sun divided its energy equally between the Northern and Southern Hemispheres.

For a variety of reasons, this could be a particularly challenging fall, for a lot of people (not just Eagles fans). But the change of seasons holds dramatic bright sides, and health experts are offering some low-cost and simple strategies to mine them.

First, they say, be aware that any sense of melancholy this time of year is normal, and how often has that term applied to anything in the last six months? Also, be aware that your mood might be darkening for reasons that transcend consciousness. And, yes, be very attuned to what you’re eating.

Unlike the spring equinox in March, when the sun is gaining power, with the arrival of fall, the sunlight is becoming ever more oblique in the Northern Hemisphere.

That’s why our shadows have mutated into stick-figure giants in the mornings and late afternoons. Plus, darkness is making dramatic gains, better than two minutes a night.

» READ MORE: End of daylight saving time: Why to love clocks falling back

“You’re losing light more rapidly than at any other time of the year,” said Norman E. Rosenthal, a psychiatrist who conducted pioneering research identifying “seasonal affective disorder,” or SAD.

The eroding light can disrupt those daily circadian rhythms that govern sleeping and eating patterns. Humans have done a remarkable job of mitigating nature’s effects, but we can’t escape them completely, says Laura Frank, a La Salle University professor who specializes in dietetics. “The circadian thing is real.”

For about 5% of the population, SAD is a serious disorder; it has moderate effects on about 15%. Women, Rosenthal said, are four times more likely to suffer from it than men. For most people, it is something to endure, even if they aren’t aware of it.

» READ MORE: Seasonal affective disorder prevention and treatment

Loss of light appears to interfere with the brain’s production of serotonin, adversely affecting people’s moods, researchers have found, and the effects intensify as days get shorter.

Rosenthal said serotonin imbalance can stimulate cravings for carbohydrates and sweets. Studies have concluded that most annual weight gain, about a pound, occurs from mid-November through mid-January, coinciding with the holidays.

But another study suggests that the porking-up process is already underway, that humans have an evolutionary impulse to store food for the winter in their fat-cell pantries.

Hundreds of subjects who kept extensive diaries found that on average they consumed 222 more calories daily during the Sept. 1 to Nov. 30 meteorological fall — Thanksgiving weekend excluded — according to a study published in the early 1990s by researcher John de Castro, then at Georgia State University.

An article in this month’s issue of the journal Obesity also warned that coronavirus-related isolation was a weight-gain risk. Frank doesn’t argue.

Frank said she gained weight during the first three months of the shutdown, which she attributed in part to the loss of routine. She has since shed the pounds.

Rosenthal agreed that the lack of routine has been debilitating, and that he and his colleagues have seen “more depression, more anxiety.” He said those feelings are also tied to the "lack of all the fun things that we associated with our normal lives.”

Frank said people shouldn’t wait for normality but recognize that “I need a routine that works during the pandemic.”

» READ MORE: 75% of young adults report anxiety or depression, and suicide thoughts rise as coronavirus pandemic wears on, CDC reports

An important step is regulating eating habits, Frank said. “It does matter what time of day you do things," she said. She recommends eating more earlier in the day, and less at night. “Try not to let yourself get super hungry, and eat a few smaller meals.”

Stay attuned to the reality that the light, it is a’changin’, said Rosenthal, and that it might be coming after your mood.

“Just recognizing this is how I am this time of the year, that’s already doing something,” he said. "Just that awareness is already the beginning of getting help for it.”

For those who want to avoid the disorienting experience of waking up in the dark, he advised buying a timer that will flick on the lights before sunrise.

Once out of bed, he said, get out early and often, and “look at the sky.”

“We are incredibly fortunate to have such a magnificent fall,” he said. And the longer nights serve an important aesthetic purpose: They play a critical role in promoting the annual foliage show, which makes our views the more spectacular.

» READ MORE: Fall foliage outlooks are bullish for colors — and leaf-peeping crowds