This research article review the key types of genetic research design, methodology involved and emerging and established finding in relation to child and childhood psychiatric disorders, and finally genetic factors seems especially important for autism and attention deficit hyperactivity disorder. (Thapar and McGuffin, 2008)1 Twin and adoption study design are now being used to examine gene environment interplay, the effects of environment risk factors co-morbidity phenotype definition and development change Liu et al (2006)11 The ways in which specific gene variant excert risk effects at cellular and biological system are proving to highly competitive (Moffitt et al, 2005).2 Finally, molecular genetic studies also high light the importance of gene environment interply, which seems to be especially important in depression and wide anti social behavior. Liu. et al)11, owen et al 2005)12 , Moffitt, et al, (2005)2