Are the Battles of Lexington and Concord considered to be a cause of the American Revolution?

No.  The Battles of Lexington and Concord are not
typically seen as causes of the Revolution.  Instead, they are seen as the first battles
of that conflict.

The causes of the Revolution are
political and economic things.  The Revolution was caused by things like the British
taxation of the colonies after the French and Indian War or the failure of the British
to allow the colonies to have enough power over their own
affairs.

The causes of a war do not tend to be battles. 
Battles are symptoms, not causes.  The causes of wars tend to be found in the realms of
politics and economics.  These sorts of political and economic changes caused the
Battles of Lexington and Concord and so we do not refer to the battles themselves as
causes of the Revolution.