If he is still suicidally depressed, this provision may cover him "You will be treated as having limited capability for work-related activities if:
you suffer from some specific disease or bodily or mental disablement and, by
reasons of such disease or disablement, there would be a substantial risk to the
mental or physical health of any person if you were found not to have limited
capability for work-related activity."
However, he may be able to qualify on other grounds. For the current provisions, see our guide to claiming ESA. However, the government is revising these and we do not have a definitive final version of the new descriptors, although the proposed ones have been published.