I've been long plagued by insomnia (runs in the family) and it has gotten worse as I've gotten older. I had hoped that taking up running would help cure it, but it didn't seem to have any effect.
I tried melatonin, but it didn't seem to help much, if at all.
I seem to have two types of insomnia: a mild type where I sort of drift in and out of a light sleep for hours. Sometimes five minutes seems like an hour and sometimes an hour seems like five minutes. I seem to wake up OK in the morning and it isn't that big of a deal, more of a nuisance.
The other type is where I feel like I'm on intra-venous caffeine (I avoid caffeine after 3:00 pm). I get jittery, can't lay still, can't relax. Very nasty.
After 20 years, I may have found the problem re: the nasty type. I hadn't had it for about a month then got it three nights in a row last week. The third night I suddenly noted a correlation that had long escaped me. Nutrasweet (aspartame).
This started around 20 years ago when I switched from regular to diet soda. Recently I had cut back on soda altogether and last week I bought some caffeine-free diet Dr Pepper and drank some the three evenings I subsequently couldn't sleep. I've been sleeping fine since.
Correlation doesn't prove causation, but I can live without diet soda. Time will tell if the nighttime jitters come back or have been banished forever.