The present invention comprises the use of an 8.9 cM region of human chromosome 18q disposed between polymorphic markers D18S68 and D18S979 or a fragment thereof for identifying at least one human gene, including mutated and polymorphic variants thereof, which is associated with mood disorders or related disorders. The invention also provides methods for determining the susceptibility of an individual to mood disorders or related disorder, comprising analyzing a DNA sample for the presence of a trinucleotide repeat expansion in the above region. Polynucleotide sequences useful for detecting the presence of such trinucleotide repeat expansions are also provided. 47 claims
MOOD DISORDER GENE