Objective: To investigate possible associations of Parkinson's disease (PD) with polymorphism in depression-related genes and in the alpha-synuclein (SNCA) gene. Methods: A consecutive series of patients with PD were divided into those with depression and those without it. Patients (330) were genotyped at four single-nucleotide polymorphisms (SNPs) in four genes previously associated with depression, as well as four SNPs in the PD-associated SNCA gene. Results: Of 330 patients, 125 (37.9%) had depression and 205 (62.1%) did not. Univariate analysis revealed significant differences between the two groups in minor allele frequency at the SNP rs1545843 in the SLC6A15 gene (p < 0.05), as well as in frequencies of genotypes and minor alleles at rs78162420 in the TPH2 gene (all p2 (OR 1.759, 95%CI 1.035-2.989, p = 0.037), AA genotype at rs1545843 (OR 1.866, 95%CI 1.017-3.426, p = 0.044), and AC genotype at rs78162420 (OR 5.036, 95%CI 1.451-17.484, p = 0.011). Conclusions: Among patients with PD, depression is associated with polymorphism at rs78162420 and rs1545843, both previously linked with depression. Our results may help clarify the pathogenesis of depression in PD. (C) 2017 Elsevier B.V. All rights reserved.