Living with a spouse with major depression is not an easy thing to do. You have to do a lot of praying and run those wedding vows through your head about a dozen times each day "for better or worse, in sickness and in health". If you really meant those at the time that you said them then that means that they are for life.
Major depression is a serious illness that can be crippling some days for those that have it. It comes with mood swings, sometimes violent, states of dark depression, loss of interest in things that the person used to enjoy, loss of sleep, changes in appetite, thoughts of suicide and more unpleasant things, both for the person suffering and for those around them.
There are medications that these individuals can take, but, like all depression drugs, these come with side effects that can be very unpleasant as well. Nausea, Diarrhea, Constipation, loss of sex drive, etc are just a few of the possible symptoms that this person may suffer from. Also, many of these drugs are only effective on about seventy percent of the people that take them and only partially helpful in some of those individuals.
Major depression, unlike other forms of depressive disorders, can last for months and may never completely go away. It can get "better" to a point, but, unfortunately, many people never completely recover. If you are living with a spouse with major depression you need to be patient, seek medical attention, be attentive and loving, but don't become a crutch or servant to your spouse. Love, honor, cherish and do your best to understand, but you must find a happy medium and give yourself time away every day in order to maintain your own mental health. It's bad enough that one of you is ill, so don't allow yourself to get down too.