It's the controversial thesis of University of Massachusetts toxicologist and school of public health professor Edward Calabrese that small doses of certain poisons may have the paradoxical effect of lengthening life spans.

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Dr Wehr suspects that the effect may have to do with a surge, during the wee hours, of certain hormones associated with the thyroid.

ECONOMIST: People, like all living things, are four dimensional

Although the imaging studies cannot determine cause and effect, it is possible that the structural changes may have come first, predisposing certain patients to depression.

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