“A Saxon king of the early seventh century, Eadbald, was described in the language of the early eighth century as troubled by frequent fits of insanity and ‘by the attack of a foul spirit’ after marrying his late father’s second wife.
But he had also rejected Christianity which his father Ethelbert had taken up, and the missionaries in Kent were going through a difficult period; so, apart from the meaninglessness of the description, some character assassination may be involved in the record.”
From p48 of Mental Disorder in Earlier Britain (ISBN 0708305628) by Basil Clarke.
Mind Hacks 