If you are talking about the Daily Digest that you get by email, you can go to your account page, and check the boxes on how often you want to get updates. If you are talking about the feed that hits your page, that is automatically generated by the site software. Anytime someone likes or comments on a post that you are following or a question that you asked, you will see that on your home page feed. As for the digest, the earliest you can get it is daily, which means that at midnight, the site sends the digest out based on the activity most related to your diagnosis.
Let me know if you have more questions, I hope this answers them for you.