Kevin Culligan, O.C.D. describes his collaborative approach to persons experiencing both depression and dark nights in the same chapter of Egan’s book, “Carmelite Prayer“:

I follow a collaborative approach to assisting others with their spiritual journey. With most persons, this assistance is primarily spiritual and religious. Following the principles of the spiritual masters, I help persons with the dryness, interior pain, and whatever else they encounter in the life of prayer. However, when signs typically associated with clinical depression—major depressive episodes, dysthymic disorders, bipolar reactions, and threat of suicide—also appear, I am prepared to consult with, and possibly make referrals to, medical or mental health professionals. I point out to persons the spiritual benefit of using these resources and assure them that I will continue to walk with them as their spiritual guide.
Following the same collaborative model, I may also point out to other helping professionals, when it seems appropriate to do so, that not all dryness or interior suffering is symptomatic of clinical depression. Medication and psychotherapy are not the best treatments for the losses of the dark nights. Indeed, persons may find that, while Prozac relieves some symptoms of depression, the spiritual dryness and interior pain associated with changing images of God and self remain.

Paradoxically, modern psychopharmacology underscores what spiritual seekers have known for centuries—that, in addition to body and mind, there is also a spiritual dimension in human life. The spirit, while interactive with mind and body, has its own rules and laws of development and is often beyond the reach of psychopharmacology and psychotherapy. And it is at this deeper level of human life—sometimes called the substance of the soul or the innermost dwelling places of the soul—that persons of prayer most consistently encounter God.