A disruption of the circadian cycle — the metabolic and glandular rhythms that are central to our workaday life — seems to be involved in many, if not most, cases of depressions; this is why brutal insomnia so often occurs and is most likely why each day's pattern of distress exhibits fairly predictable alternating periods of intensity and relief.
— William Styron, Darkness Visible: A Memoir of Madness, Vintage 1992, (p.26)
My cycle was more similar to Styron's than to what he cites as typical. He writes, "Most people who begin to suffer from the illness are laid low in the morning, with such malefic effect that they are unable to get out of bed. They feel better only as the day wears on. But my situation was just the reverse. While I was able to rise and function almost normally during the earlier part of the day, I began to sense the onset of the symptoms at midafternoon or a little later — gloom crowding in on me, a sense of dread and alienation and, above all, stifling anxiety." (pgs. 11-12)
But this was never hard and fast, and it evolved over the years. I shared Styron's rhythm during my decades of "high functioning". Daylight: good. Moonlight: bad. During the earlier period of teenage onset it was the other way. Over the two years of breakdown it was all bad, all the time. As it was again, later at onset in middle age.
The symptoms evolved as well. As a teen and a "high functioning" adult the feelings of dread and alienation and anxiety were frequently trumped by intense agitation. I was mentally alert but physically there were electrical shocks jolting my poor battered bones, so that from time to time I'd literally leap up at 3am for a run around the park. It was the "brutal insomnia" Styron emphasizes but it was more, a crayzass surge of overwhelming somatic compulsion which took sleep entirely off the agenda. Instead of tossing I learned to be productive, reading books mostly. I've read a lot of books. It's not that I read quickly, 'cos, I sure don't. It's that I was seldom sleeping, so there was a ton of available time.
And yet, from my breakdown onward, there was also intense collapse into unconsciousness, almost narcoleptic, where setbacks or triggers sent me immediately to bed. I could sleep any time if something upset me. I'd feel the bottom of the world open underfoot, and learned through experience that the most effective way to close that trapdoor was to hit the pillow. Often for thirteen or fourteen hours. I'd wake feeling, not refreshed, and certainly not calmed, but leveled-out, meaning, less extreme in either direction. This was why heroin was so helpful during the breakdown. I'd pin my eyeballs and feel level while more or less awake. Kids, don't try this at home. But, with apologies to the DEA and the statute of limitations, it was undeniably helpful at work.
These symptoms and these periods share the main thing: intense sleep disruption. Nearly always a primary indicator of depression.