I'm the husband of the rarer marriage where the wife has ADD, which was formally diagnosed a few years ago.  What I did helped and I believe that it can help regardless of the genders.

I am analytical by nature.  To truly drive me insane, make me execute the same failure repeatedly without being allowed to change anything for better or for worse.  I noticed that things were cyclical.  Not just the every 28 days cyclical, but a much longer period of highs and lows.  I can't just ride the waves because the lows were both intolerable and we have two young children along for the ride.

(note:  this is premise/background and is NOT the great idea I wish to share) I had grown tired of the rollercoaster and took the brunt of it by not letting myself get caught up in neither the highs nor the lows.  I found that one way to speed up the low side was to pretend like it all hit me deep and that it was, yet again, the end of our marriage.  I also found a way to extend the highs - by keeping her at arms length for the time that she was aware of and paid attention to how she treated others.  You may call it manipulation and I would agree.  I only justify it by using it only as a way to weather the storm and delay the next one.

After I while I knew that the manipulation only helped me/us tread water and that it wasn't a sustainable long term solution.  We are fortunate that she is seeing a counselor about her ADD, yet this turmoil continued unabated.  I made a bold move and asked my wife if I could discuss my experiences with her counselor in hopes of getting to something sustainable.  I also asked to do this alone because I didn't want her to sit there and get bashed for an entire session.  I would lose some candor, and I wouldn't want to be there if the tables were turned.

When I went in, it was made clear that I was there to share my observation of her behavior for her benefit.  I told her counselor of my manipulation. its purpose, and how I would prefer to no longer require it.  I had a long list of both gripes and observations.  I also spoke about the two previous marital counseling sessions that identified work she needed and failed to do, and that I will be willing to give marital counseling a third try only after she has done at least some of that work.

Her counselor told me that it took courage for me to come in.  I have thought about that statement for months since we met and still don't understand how it was courageous.  Maybe I'm just beat to the point that I fear a divorced family for two children more than anything else.  I guess I don't call it courage when one acts out of desperation or is exercising what few options remain.

Keep in mind that I had to keep any suspicions or amateur diagnoses to myself because, coming from me, it would be an accusation and deemed entirely improbable!

The counselor recommended a psychologist who performed some basic tests.  When she told me she got the results, I asked her if it was manic-depressive or bipolar.  It was bipolar.

So my recommendation, if you have a spouse currently getting help, is to try to meet with your spouse's professional.  The professional would only have your spouse's interests in mind - so share what's going on at home and in your lives from your front row seat.  The time goes fast. so only tell about your observations, your actions and the responses they generate.   I would hope/expect that the professional would take it all in, prune out your bias the best they can, and distill some objective information about how their patient is operating on regular basis.