Well, yes, anxiety can cause dark circles under your eyes. Maybe you can not believe this. But according to some researches, it does cause the dark circles under your eyes. As we know that when you are anxious, you will feel stressed and also this can make some disorders in your body. In this way, you will not sleep well. And then it can lead to dark circles. So you should just pay more attention to it. To treat them, you can drink more lemon juice, olive oil which can be good for your eyes. Also, there are many other factors that can cause dark circles under eyes, such as the allergy and alcohol, lack of sleep. For your situation, lack of sleep is the big problem. So you should also pay attention to it. If the situation is serious, maybe you can go and ask the doctor to help you. Of course, you can also eat some watermelon which has the same effect on your eyes.