Review article
What have we learned from genome wide association studies in psychiatry?

Genetic epidemiological studies have shown that psychiatric disorders such as schizophrenia and bipolar disorder (BD) are highly heritable. Genome wide association studies (GWAS) involve the use of arrays that simultaneously genotype several hundred thousand single nucleotide polymorphisms (SNPs). GWAS is hypothesis-free search of every gene and intragenic regions of the genome. GWAS have reported genome-wide significant associations of common variants for schizophrenia and bipolar disorder. Many of the risk alleles identified in GWAS of schizophrenia such as ZNF7804, MHC, and NRGN are also implicated in BD. Also risk alleles for BD such as ANK3 and CACNA1C have been implicated in schizophrenia. It has been suggested that bipolar disorder with psychosis may be the clinical manifestation of genes overlapping between SCH and BPD. Copy number variants (CNV) are found at increased frequency in neurodevelopmental diseases – schizophrenia, autism, attention-deficit hyperactivity disorder and intellectual disability. It is possible that CNV can result in disturbed brain development and in this way lead to increased susceptibility to different neuropsychiatric disorders, dependent on additional environmental and genetic factors. The identification of disease-associated genes will increase our knowledge of the pathophysiology of psychiatric disorders. The identification of biological pathways has the potential to revolutionize diagnostics and treatment. This review summarizes recent research progress in GWAS studies in psychiatric disorders such as schizophrenia and bipolar disorder.