Our results further indicate that the heritability of neuroticism likely consists not only of common SNPs with small additive effects. Common SNPs with non-additive effects, rare SNPs and indels may also influence neuroticism, possibly in interaction (epistasis). As a consequence, to further our understanding of the genetic and molecular basis of neuroticism (and associated psychiatric disorders) different routes need to be taken in future studies. One route would be to increase the number of subjects and SNPs to further identify more common variants of additive effect, which has shown to be successful for schizophrenia.60 Also, the study of variants other than common variants of additive effect could be pursued. Alternative routes could include pathway analyses and genetic studies that are informed by results from the animal literature on basic emotions such as fear, sadness and anger.61–64
