Edadh is a symbol for altered states of consciousness and awareness:

From eDIL(http://tinyurl.com/53oczj):

"ibine . . . arroichled iarom edhad as co nderna ibne de an `i' has been
taken from it , Corm. Y 1301 (see edad). is deamna rom aircellsat leo `it
was demons that spirited me away with them ', Todd Nenn. 210.5 . "

Call out to the gods and you will be "spirited away by demons" or, more
practically, you will experience altered states of consciousness.

Edadh is seen as being "brother to birch" because the birch tree (Beith) and
its own kenning is seen as a metaphor for the struggles of being born and
coming into this life in a physical way. It is the battle for life. It is
the white tree above the once blacked soil of the fires. Conversely, being
"birched" is one of the eight-fold-ways that some esoteric practices use to
alter states of awareness. The use of drugs is another

If one looks at Ogham as a sequence in states of consciousness, here are
some insights I use in my own work based on the Ogham-Druidic kennings for
the vowels:

A (Ailm) - "First and the Last" - the birth of awareness (i.e. child
luminosity, "A