This article from NewsTarget describes an omega-3 deficiency that can cause that condition.
Boschman believes that the lack of the essential fatty acid in pregnant women might be a cause of both postpartum depression and the development of
symptoms popularly diagnosed as ADHD, Tourette's syndrome and even mental retardation in the delivered child. During pregnancy, almost all of a
woman's omega-3 reserves are used to form the brain of the developing fetus. If she doesn't increase her intake of the essential fatty acid
accordingly, postpartum depression can occur. Additionally, if her body lacks enough omega-3 to form the fetus' brain sufficiently, and the child is
not given proper omega-3 through diet or supplements during the first two years of life, then Boschman believes one of three brain disorders will
occur, depending on the severity of the deficiency:
ADHD (relatively less deficient)
Tourette's syndrome
Mental retardation (severely deficient)
In this sense, these three brain disorders are part of the same continuum, all with the same root and the same necessary preventative measure.