Your vivid dreams are interesting. I have been under treatment for insomnia for years. When I first started getting not just sleep, but quality sleep, I was having freaky dreams. It scared me a little at first until my doctor told me to keep a careful journal not necessarily of content of dreams, but of perceived duration, exactly how freaky they were on a scale of 1 to 10, and how long it took me to feel OK after I woke up, and the also to record how rested and functional I felt during the day.
Eventually I discovered that vivid and subjectively long dreams translated to quality sleep that made me feel rested and alert the next day.
Now, there is a relationship between depression and insomnia that hasn’t been quite teased out-- that is, it’s a big debate which one causes the other (I’m firmly in the camp of “sleep deprivation causes depression”), and it wouldn’t surprise me at all if people on antidepressants experience vivid and possibly frightening dreams they are not used to when they first start on medication, because they have been lacking in REM sleep for a long time.
I have two sleep studies that show REM sleep disruptions-- my doctor said it was as though I was such a light sleeper that the act of going into REM sleep woke me up sometimes.
Anyway, there might be some tossing and turning while a person adapts to the effects of the medication on sleep-- once you do adjust, you might need less sleep. But the initial adjustment might be upsetting, and might even make sleep deprivation worse.
Everyone I know who has started on an antidepressant has started on a dose below actual clinical effects, and they stay on that for like a week, to check for side effects and allergic reactions, then they start on a therapeutic dose, but it’s still very low. It might be six weeks before they are taking a really effective dose, but none of them has ever had anything untoward happen.
I wonder if the people who were test subjects were put on a higher dose right away: it makes the trial period shorter (thus cheaper), and it ferrets out serious side effects that are going to get the company sued (like, don’t give the drug to people with peanut allergies).