Major Depression and Manic-Depression . Any difference?

Countless number of patients and their family members have asked me about manic–depression and major depression. "Is there any difference?" "Are they one and the same?" "Is the treatment the same?" And so on. Each time I encounter a chorus of questions like these, I am enthused to provide answers.
You know why? Because the difference between these two disorders is enormous. The difference does not lie on clinical presentation alone. The treatment of these two disorders is significantly distinct.
Let me begin by describing major depression (officially called major depressive disorder). Major depression is a primary psychiatric disorder characterized by the presence of either a depressed mood or lack of interest to do usual activities occurring on a daily basis for at least two weeks. Just like other disorders, this illness has associated features such as impairment in energy, appetite, sleep, concentration, and desire to have sex.
In addition, patients afflicted with this disorder also suffer from feelings of hopelessness and worthlessness. Tearfulness or crying episodes and irritability are not uncommon. If left untreated, patients get worse. They become socially withdrawn and can't go to work. Moreover, about 15% of depressed patients become suicidal and occasionally, homicidal. Other patients develop psychosis—hearing voices (hallucinations) or having false beliefs (delusions) that people are out to get them.
What about manic-depression or bipolar disorder?
Manic-depression is a type of primary psychiatric disorder characterized by the presence of major depression (as described above) and episodes of mania that last for at least a week. When mania is present, patients show signs opposite of clinical depression. During the episode, patients show significant euphoria or extreme irritability. In addition, patients become talkative and loud.
Moreover, this type of patients doesn't need a lot of sleep. At night, they are very busy making phone calls, cleaning the house, and starting new projects. Despite apparent lack of sleep, they are still very energetic in the morning — ready to establish new business endeavors. Because they believe that they have special powers, they involve in unreasonable business deals and unrealistic personal projects.
They also become hypersexual — wanting to have sex several times a day. One–night stands can happen resulting in marital conflict. Like depressed patients, manic patients develop delusions (false beliefs). I know a manic patient who thinks that he is the "Chosen One." Another patient claims that the President of USA and the Prime Minister of Canada ask for her advice.
So the big difference between the two is the presence of mania. This manic episode has treatment implications. In fact the treatment of these disorders is completely different. While major depression needs antidepressant, manic-depression requires a mood stabilizer such as lithium and valproic acid. Recently, new antipsychotics, for example risperidone, olanzapine, and quetiapine, have been shown to be effective for acute mania.
In general, giving an antidepressant to manic–depressed patients can make their condition worse because this medication can precipitate a switch to manic episode. Although there are some exceptions to the rule (extreme depression, lack of response to mood stabilizers, among others), it is preferable to avoid antidepressants among bipolar patients.
When considering the use of antidepressant in a depressed bipolar patient, clinicians should combine the medication with a mood stabilizer and should use an antidepressant (e.g. bupropion) that has a low tendency to cause a switch to mania.