My WS also had severe depression, and started meds just after D-day. He was also diagnosed with ADHD. Up until then he had been self-medicating with alcohol (not very smart).
After starting on anti-depressants, and seeing his IC, his whole outlook and attitude changed for the better. It took about 6 weeks for the meds to work, but it was worth the wait. The only downside (if you can call it that) was that when he began to realise that all of the things happening around him were BECAUSE of him, he got really angry at himself, and his IC spent a lot of time helping him with self-hatred and negative self-talk.
7 months out, and things are going really well, but without the meds and IC, I really don't think we stood a chance.