Living in France, I am sometimes asked about Cédric Villani, a very popular figure here. Will he come back to mathematics ? The question becomes more relevant with the coming parliament elections (he should not candidate, having split with the president's party).
My impression is that it would be difficult for him. Even after a two-weeks vacations, I find a bit difficult for me to think hard on a mathematical problem ; I just cannot imagine stopping a year long.
Are there examples of mathematicians who stopped mathematics for a while (at least several years) and then resume and achieved valuable results in their second career ?
Notice that the break may have various causes, such as nervous breakdown, imprisonment, war time, ... Of course, Jean Leray doesn't count, as he kept doing maths in an oflag (and what maths !).
Besides the case of women who stopped because of motherhood (I should have think of it from the beginning ; thanks to Fedor), let me mention that of chinese mathematicians who were sent to the countryside during Cultural Revolution (e.g. Hsiao Ling).