Objectives: Several studies reported decreased quality of life (QoL) and sleep as well as increased rates of depression for patients with pituitary adenomas. Our aim was to explore to what extent differences in depression and sleep quality contribute to differences in QoL between patients with pituitary adenomas and controls. Design: A cross-sectional case-control study. Setting: Endocrine Outpatient Unit of the Max Planck Institute of Psychiatry, Munich, Department of Internal Medicine, Ludwig-Maximilians-University, Munich, and the Institute of Clinical Psychology and Psychotherapy, Technical University, Dresden. Participants: Patients with pituitary adenomas (nZ247) and controls (from the DETECT cohort, a large epidemiological study in primary care patients) matched individually by age and gender (nZ757). Measurements: Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI) and QoL was measured by the generic EQ-5D and calculated by the time trade-off-and VAS-method. Depression was categorized as 'no depression', 'subclinical depression', and 'clinical depression' according to the Beck Depressions Inventory for patients and the Depression Screening Questionnaire for control subjects. Statistical analyses: General linear and generalized, logistic mixed models as well as proportional odds mixed models were calculated for analyzing differences in baseline characteristics and in different subgroups. Results: Patients with pituitary adenomas showed decreased QoL (VAS index: 0.73G0.19) and sleep (PSQI score: 6.75G4.17) as well as increased rates of depression (subclinical or clinical depression: 41.4%) compared with their matched control subjects (VAS index: 0.79G0.18, PSQI score: 5.66G4.31, subclinical or clinical depression: 25.9%). We have shown that a substantial proportion of the reduced QoL (48% respectively 65%) was due to the incidence of depression and reduced sleep quality. Conclusions: These findings emphasize the importance of diagnosing depressive symptoms and sleep disturbances in patients with pituitary disease, with the ultimate goal to improve QoL in patients with pituitary adenomas.