Background The CACNA1C protein is a L-type calcium channel, which influence affective disorders. Purpose The purpose of the present study was to examine the possible association between the different genotypes of rs100677 CACNA1C gene and anxiety and other clinical symptoms in patients with unipolar depression. Patients and controls A total of 754 patients and 708 controls from the Danish Psychiatric Biobank participated. Results A significant correlation was found between anxiety and the A allele. It was further found that patients with the A allele more often were treated with electroconvulsive therapy and patients with the AA phenotype had the highest age. Limitations The only information about controls was their sex and that they were recruited from the blood bank. Two types of inclusion criteria were used. The clinical data were not complete for all patients.