Most child and adolescent psychiatric problems are multifactorially determined. This means that, whenever discussing aetiology, both biological, social and psychological factors have to be taken into account.

It goes without saying that, with a definition of child neuropsychiatry such as the one given in Chapter 1, biological factors are of crucial importance in all cases falling within this subbranch of child psychiatry. Even so, social and psychological factors are often of major importance, too.

This chapter deals briefly with some of the major issues in the field of aetiological and pathogenetic factors in child neuropsychiatry. It is divided into five different sections: (1) genetic factors, (2) reduced optimality in the pre- and perinatal periods, (3) major environmentally determined brain damage, (4) sociocultural influences and (5) psychological factors.

Genetic factors

The influence of genetic factors on the child's intellectual, emotional and behavioural development is widespread and very important (Plomin, 1994). However, for many years, and especially during the 1960s, 1970s and early 1980s, the contribution of genes to the psychiatric disorders of childhood was grossly underestimated in many clinical settings. With the advent of appropriate twin, adoption and family studies, and, in particular, following the development in the new genetics (with more and more sophisticated methods for studying genes at the DNA level), the under-emphasis of genetic factors has, almost too drastically, been turned into a strong emphasis. Sometimes, one has almost sensed an over-reliance on genetic factors when trying to account for various mental and behavioural phenomena.