As it did to so many, the news of Robin Williams’s death came as a great shock to me. How could a man with such talent and charisma who brought me to tears, both of joy and sadness, on so many occasions be gone so suddenly? Then details of his depression came to light, and I understood. The National Alliance on Mental Illness estimates that 6.7 percent of American adults live with major depression, and 2.6 percent of all American adults are afflicted by bipolar disorder. I understand, because I am one of them.