The study with the use of the CES-D scale revealed the combination of depression and metabolic syndrome in 24% of the examined patients. The HADS scale showed depression in 16% of the interviewed patients. Based on the two scales, depression was documented in 32% of the patients. The chance of development of metabolic disorders in case of depression was estimated as 2.4 (95%); CI--1.3-4.6. Urinary 6-COMT level at 4.00 correlated with its total nocturnal and daytime concentrations and with sleep disorders (r = -0.41; r = -0.48; r = -0.43 respectively). Daytime sleepiness correlated with the daytime 6-COMT level (r = -0.32). The score values by the CES-D scale correlated with daytime 6-COMT level (r = -0.23). Multiple regression analysis showed that reduced melatonin level deteriorates quality of nocturnal sleep and increases the risk of depression (R = 0.4. coefficient β = -0.413 (p<0.04) and F = 4.5).