When Alison Malmon was a freshman at the University of Pennsylvania, her older brother Brian took his own life. He had kept up a good front at Columbia, doing well academically, singing in an a cappella group, working on the college newspaper. He had struggled with mental illness in solitude. His friends had the sense that something was wrong, but acknowledged later that they hadn’t known what to say or do. “He had kept it quiet because he was afraid and ashamed,’’ Malmon says now, over a decade later. “Afterward I wondered: if he had sought help sooner, could his death have been prevented?’’ Joan Wickersham j.wickersham@comcast.net