As I understand it, the research is not completely conclusive but the claim is that there is significant habituation effect. I've also heard that restlessness/i

As I understand it, the research is not completely conclusive but the claim is that there is significant habituation effect. I've also heard that restlessness/insomnia are just as likely to be caused by withdrawal effects in the evening as they are by high consumption. Withdrawal effects have similarities to high usage, and anecdotally if I'm drinking a lot of coffee but stop early in the day I often have problems sleeping.