Is bilingualism a handicap?

Is bilingualism a handicap? The literature on the effects of bilingualism on the intelligence, linguistic proficiency, and mental health of bilingual individuals is vast, complex and contradictory. The perusal of almost any random collection of articles, treatises, and opinions on the topic would lead most lay readers to the conclusion that the question as to whether bilingualism is a handicap has much in common with that as to whoso had taken the Pobble's toes: nobody knew, and nobody knows. The only certain thing is that it is a condition which either afflicts or benefits a very large proportion of the world's population, and cannot be ignored even in such a bastion of English monolingualism as New Zealand.