Immigration more risky for small children?

Apparently latest research claims that immigration at a young age is associated with an increased risk of psychotic disorder such as schizophrenia. Furthermore, "those who immigrated when under the age of five had a twofold higher risk than those who immigrated at age 10-14 years, and a threefold higher risk than those who immigrated as adults." Pretty interesting finding. I always thought that the younger one is, the better he/she adapts... but I suppose adaptation and mental health are not identical things. Hmmm... something to ponder on.