Neurosci Biobehav Rev 80: 555 - 572, 2017. doi: 10.1016 / j. neubiorev.2017.07.002 Symptoms and Signs of Depressive Disorders Depression causes cognitive, psychomotor, and other types of dysfunction (eg, poor concentration, fatigue, loss of sexual desire, loss of interest or pleasure in nearly all activities that were previously enjoyed, sleep disturbances), as well as a depressed mood.