CLOCK and depressive symptom measurement: Single nucleotide polymorphism (SNP) analysis found polymorphisms in Bmal1 and other genes that were potentially associated with increased risk of seasonal affective disorder and AD [100–102], while genome-wide association studies revealed a large overlap (> 80%) in the genetic factors involved in bipolar disorder, depression and schizophrenia, including hundreds of significant genetic loci [103], several of which were related to clock genes.