About one-third of depressed patients will have EEG abnormalities, but EEG is only a necessary test for the identification and diagnosis of depression, especially to exclude organic diseases such as epilepsy, but most depressed patients have no obvious abnormalities or only minor abnormalities in EEG, which have no special clinical significance. About one-third of depressed patients have abnormal EEG mainly presenting as low flat alpha waves, and the brain function shows low functional EEG changes, which is related to slow thinking, low brain activity and poor psychomotor activity in depressed patients. In general, it is best to follow medical advice and arrange for a detailed examination. If the EEG already shows these changes, psychological testing should be continued to confirm the diagnosis of depression.