My heart goes out to you. I can't even imagine the heartache and despair you are experiencing at this time.
My thought has been that depression is such an all encompassing disease, that one of the best ways to tackle it is to go at it from all angles. So, in my humble opinion, your question is an excellent one.
No doubt, medication is the top treatment choice. But, I do believe that vitamin supplements can help play a role...perhaps a contributing one and in the end, forces working together I think might make for a positive difference.
What has helped me significantly with depression is taking a B50 tablet and 5000 mcg of B12. I know my doctor recommends that people with severe depression take a B100 tablet.
Additionally, fish oil tablets and vitamin D can also be helpful.
Many people who suffer with Bipolar Disorder say they have received benefit from a vitamin co. called True Hope...although there is some controvery there.
Regular exercise is very good. Of course, when one is in a bad depression, it is next to impossible to participate in exercise. I see exercise as almost a preventative tool. Personally, I enjoy the way I feel so much and see the benefit(s) so much, that I am very motivated to continue exercising.
In addition, make sure your husband is getting his sleep each night. Is he taking anything for sleep? Both my husband and I take L-Tryptophan as needed and have found it to be a blessing.
Does your husband like to journal? Does he see a therapist regularly?
Does he have any regular hobbies?
How are your husband's relations with others???? What about family therapy? What about systems therapy?
Even though I am not a drinker due to my headaches, I have found reading the words of AA and related groups very helpful when treating depression. There is much wisdom there.
Prayers and hugs going out your way.