Could you tell me what are leads to of autism and asperger's syndrome?

Combo of factors: Most cases of autism appear to be caused by a combination of autism risk genes and environmental factors influencing early brain development. Over the last five years, scientists have identified a number of rare gene changes, or mutations, associated with autism. There is more work to be done, however, we know more today than ever and the research is promising.

Autistic Spectrum: Disorder is the diagnosis now for the neurodevelopmental disorder characterized by qualitative impairments in social communication & social reciprocity + narrow, restricted areas of interest or repetitive, nonfunctional movements. Etiology is multifactorial. Many genetic & epigenetic factors are known; the latter, like low folate (folic acid) at conception, alter function but not structure or sequence of genes