SLC6A4 and Anxiety: A study found no association between current anxiety and depressive symptoms in COPD patients (n = 302) with a polymorphism in the SERT gene in the promoter region (5-HTTLPR) and intron 2 variable number tandem repeat (STin2VNTR, 9, 10, or 12-repeat alleles); however, the polymorphism was associated with previous anxiety and depressive episodes [103].