Background: The seven papers in this special section chart where we are in the quest for quantitative trait loci (QTLs) in key areas of child psychology and psychiatry such as reading and hyperactivity. But we are not there yet.
Methods: This commentary considers some new developments that are likely to accelerate the journey towards the identification of QTLs.
Results: The single most important factor is the need for very large samples to attain adequate power to detect and replicate QTLs of very small effect size. Another important development is the microarray, which makes it possible to genotype hundreds of thousands of SNPs simultaneously. Using microarrays in association studies allows SNPs across the whole genome to be genotyped. Microarrays will boost power even more when they contain all functional polymorphisms in the genome, including functional non-coding DNA.
Conclusions: Once replicable QTLs are identified in areas such as reading and hyperactivity, the real journey will begin. Future studies will use sets of QTLs as genetic risk indicators in top-down behavioural genomic research, leading to gene-based diagnoses, gene-based treatments tailored to the individual, and early warning systems and interventions. These discoveries will eventually help to prevent or at least ameliorate childhood disorders before they cast their long shadow over development.