Several psychiatric disorders including Schizophrenia, major depressive
disorder (MDD), bipolar disorder, attention-deficit/hyperactivity disorder and autism
spectrum disorder are all very common. WHO data suggest MDD as a leading cause of
adult disability, however the complex nature of the disease etiology makes it least
understood among its more studied disease counterparts. Although both genetic and
environmental factors are known to contribute substantially to the etiology of MDD,
several association studies both single gene and Genome Wide Association Studies
(GWAS) are available describing the contribution of multiple genes. Severe lacunae
exist in correlation among these association studies that prevent a clear definition in
genetic causes that could be a result of small samples, epigenesis, heterozygosity in
populations studied, presence of rare variations as well as lack of proper co-relation
with environmental factors. With the advances in nucleic acid and amino acid
sequencing techniques in this era of genomics and proteomics, the identification of
novel disease markers is easier. More extensive study identifying rare variations in
larger population along with a more systematic study including system pathways as well
as genetic and protein interaction is recommended to obtain a clear picture of the
underlying genetic causes of these complex disorders.
Keywords: Biomarkers, Candidate genes, Depression, Epigenetics, Genome
Wide Association Studies (GWAS), Genomics, Major depressive disorder
(MDD), Pharmacogenetics, psychiatric disorders, Serotonin transporter (5HTT).
