Interestingly, C15orf53 has previously been associated with bipolar disorder and alcohol dependence, and FBXO33, which may be involved in autism spectrum disorders, was highlighted in the previous SNP-based GWAS that we performed in the same discovery dataset and provides additional evidence supporting the ubiquitination machinery as a new mechanism for ADHD7, 22. This evidence concerns the gene FBXO33 and bipolar disorder.