Depression is a syndrome of persistent and significant depressed mood, decreased interest, insomnia, decreased appetite/weight loss, fatigue, decreased energy, feelings of low self-esteem, decreased memory/distraction/hesitation, suicidal ideation or behavior for more than 2 weeks. However, there is no history of manic episodes. Mild mania or mania is defined as more than 4 or 7 days of high, excited mood, high energy, increased activity, arrogance, exaggeration, talkativeness, decreased need for sleep, recklessness, impulsiveness and irritability, excessive spending or making irrational investments, and planning a lot. The word mania sounds derogatory in Chinese, as if it means madness. In fact, the word Mania is difficult to translate exactly, and originally means a state of excessive excitement, activity, and euphoria. Mania and depression are two completely opposite extremes, two clinical phases, so patients who have both conditions are called bipolar disorder. If a depressed patient has the experience of (mild) manic episodes, he or she should be diagnosed with bipolar disorder, which is a disorder of alternating depressive-manic episodes. The depressive phase of bipolar disorder is called bipolar depression. In short, depression with mania is bipolar depression, and depression without mania is depression. Depressed patients who have never had a manic episode do not mean that they are not bipolar disorder, especially for young patients, often the symptoms of mania have not yet appeared, and once they do, they should promptly seek medical advice to change the original treatment. 1, bipolar depression and depression (from depression without manic episodes) treatment drugs are different and not a disease, although the performance can be exactly the same, for example, are depressed mood and reduced interest. 2, bipolar depression is sometimes different from depression symptoms of depression in some characteristics. For example, bipolar depression is often drowsy and weight gain. Depression is usually insomnia and weight loss. If drowsiness and weight gain are suspected to be bipolar depression. 3. Bipolar depression tends to start earlier than depression, and depression often appears before the age of 25. 4. Bipolar depression often starts suddenly, unlike depression which has a developmental process, and bipolar depression often does not have any triggers, while depression often has some life triggers. Depressed patients who get excited after taking antidepressants often belong to bipolar depression. True depression on antidepressants does not excite. Seasonal episodes of depression should be suspected as bipolar depression. Some patients are depressed in winter and manic in summer. When depressed, they have low self-esteem, pessimism and suicide attempts, and when manic, they are arrogant, blindly invest and spend most of their family fortune. The diagnosis of bipolar depression often relies on the doctor asking the patient about the history of manic episodes, and the patient often does not remember the experience of manic episodes, because mania is often a good feeling, unlike the experience of depression which gives a deep impression. Bipolar depression should not be treated with antidepressants alone, which can induce manic episodes, and one or two mood stabilizers need to be taken at the same time. The course of antidepressant treatment for bipolar depression is short, usually 3 months or less, unlike depression which needs to be treated for more than 9 months, but the course of application of mood stabilizers is longer, for the first episode, and needs to be maintained for at least 1 year, otherwise it is extremely easy to relapse.