Sharon Salzberg, 58, a co-founder of the Insight Meditation Society, has spent more than three decades helping Westerners access a daily spiritual practice that originated in Buddhism but is not confined to that faith.

When Sharon Salzberg returned to New York from her first trips to India in the 1970s, a crinkled cotton blouse was still exotic and people would politely sidle away from her at parties after she told them she taught meditation for a living.

Now even Starbucks sells chai (a milky Indian spice tea), and a landmark Massachusetts General Hospital study released last month has documented that the brain shows positive physical changes — in density of gray …