Cortisol might be the cause.. Cortisol is the hormone that makes us feel alert, it can sometimes be elevated at night when we are under stress or lead stressful lives. Also it is elevated when our blood sugar is low (our body uses cortisol to RAISE blood sugar). So if you have not eaten for a long time, or have eaten a sugar loaded meal, then when the crash comes your body will use cortisol to raise the sugar level in your blood, keeping you awake at night. This is important, because your body's blood sugar level can lead even to death if it goes out of the parameters your body/brain needs, so your body prioritises this. A sugary diet or not eating well can lead to problems, as your body will prioritise its blood sugar levels over sleep (and that is saying something!). Also caffeine (as most know) should be avoided, but I recommend giving it up entirely. Read "the truth about caffeine" or a similar book, if you need convincing. Phosphatidylserine, a natural substance we produce in our bodies as well as getting from a some foods can really help us reabsorb cortisol when its high, so this can be helpful, but only if you sort out your diet too, Supplements of this could help if taken after dinner, I was recommended 300mg a night by functional medical practitioner and it was very effective, I however suggest getting some nutritional advice or advice from a functional medical practitioner before undertaking any supplement program. Hormone problems related to your thyroid can also make a difference to your sleep quality, and so if you are experience lack of energy (which I bet you do) then check out your thyroid. Docs normally won't treat you if your TSH (a thyroid marker they look at) is below 5, but if its over 2 you will not feel good (I know this from my own experience and that of others I have spoken to). If your TSH is over 2 then go and see a functional medical practitioner (please learn the difference between them and regular doctors) and you will be on the right track. Not all sleepless nights are caused by universal factors or the ones I've mentioned, my information is for you to bear in mind and use your judgement. Magnesium deficiency can really harm a good night's sleep, so my last words on the subject are to try a little magnesium after dinner (magnesium is the most deficient nutrient in modern society) so its likely it could help. You can take it through supplement tablets, a body spray on the skin, or baths with salts high in magnesium. They all work. Magnesium is the first thing given to heart attack patients to calm everything down, so you can imagine its importance, and also its safeness, please read up on it or take advice before proceeding with any supplements though. I hope you find this information useful, I have obtaining from wide reading, discussions with functional medical practitioners and nutritionists, and lastly but not least, through first hand experience.