St. Johnswort Keeping Me Awake

I would like to know what things that St. John's Wort reacts with? I was taking it to relax my nerves which was helping my back and relieving the pain. I started taking another brand and it seems to keep me awake all night. Do you have the answer to my question?

There are many reasons why St. Johnswort could be affecting you differently. Everything from differences in the way that the two products are formulated, differences in doses, interactions with other herbs or drugs you may be taking, to differences in your health before and now could be keeping you awake. Or, perhaps there is something you are taking or doing that is keeping you awake now. You should consult a competent herbalist for help in sorting out which may be the cause.