For years, your dad has enjoyed golf, but now he turns down every invitation. If you suspect depression, you may be right. A loss of interest in just about everything is a common symptom of depression. "You may see decreased pleasure in activities that used to bring enjoyment," says Michael Garrett, MD, vice chairman and professor of Clinical Psychiatry at SUNY Downstate Medical Center in Brooklyn. "A grandparent who usually has a joyful response to a grandchild may now show indifference, an avid photographer is not photographing, a biker is not biking."