Symptoms - Vague uneasy feelings.
This is when you have a fear of unknown things. Or perhaps you might feel that something bad is going to happen, but you don't know what. The type of people who need aspen are those who tend to be more sensitive to outside influences. Part of them is tuned into other dimensions or worlds, but they are unable to tell the source, so they pick up things that others might not.
I often prescribe this remedy for those who have panic attacks of unknown sources, or demonic visions while meditating. Also for those who feel that something bad is going to happen, either locally or on a global scale.
It's also useful for fear of things that go bump in the night, or uneasy feelings when you walk into a room or meeting someone.
It is a very potent remedy for an empath who will often pick up on things that are happening, but they have no idea of the cause or the source behind it.