Genetics of attention deficit/hyperactivity disorder: are we ready for molecular genetic studies?

Reports of possible genetic associations or linkages for attention deficit hyperactivity disorder are appearing at an increasing rate. As with many other neuropsychiatric disorders, claims of positive findings are frequently followed by negative reports. In this review, the evidence underpinning genetic hypotheses for the origins of ADHD is reviewed with particular emphasis on what is the heritable phenotype. It is concluded that advances in identifying mutations or allelic variations in genes predisposing to ADHD are likely, but the general replication of such findings must await a better characterization of the heritable phenotypic elements of ADHD and a better understanding of its genetic heterogeneity.