Millennials really are different; they're too much focused on work, according to new research, and they're pessimistic, too.

The Harvard Business Review reported that "millennials are obsessed with their jobs, socialize with friends less often than many older folks assume, and don't seem to set much store in developing a spiritual life."

That determination arose out of the application of big data to the results of a previous study by New York City-based social technology company Happify, which had found that people in their twenties and early thirties are in a relatively negative state of mind — suffering a sharp increase in ongoing stress, characterized by the most negative thoughts and the least positive emotions, compared to other age groups.