The crucial aspect is to face it head on rather than sweep it under the carpet. There are many therapies available.
Recently a reader of the magazine I edit, Life Positive, called me to find out if I could help him find possible cures for his sister who has been battling chronic depression for two decades. Taking care of her has consumed the time and energy of her aged parents and he himself had deferred from marrying until quite recently so he could support her. He too, he confessed, had suffered from the dreaded malaise, until he took himself in hand, went to a therapist and worked his way out of its hold.