When asked if they had a history of depression, the roles of these two professions flip-flopped. Managers were the lowest, at 8.9 percent, with transportation workers clocking in at 9.2 percent.

"The act of leading may contribute to a lower rate of depression among managers overall, compared with those not in managerial or leadership positions. Or, it may be that those who naturally act as leaders, and who are often then promoted to the role of manager, are people less likely to suffer from depression," Gallup said by way of offering some explanation for its discovery.

So which professions experience depression more often than others? The highest rates of current depression were reported by nurses (6.1 percent), service workers (6 percent), teachers (5.9 percent) and non-teaching/medical professionals (5.9 percent). Physicians, clerical and production workers also reported relatively high rates.

The same general trend prevailed when people were asked about a history of depression. However, teachers, physicians and nurses ranked somewhat lower, suggesting that their professions may contribute to depression occurring later in life.

In general, Gallup said, the study suggested there's something about certain professions, and work in the service industry, that is related to depression.

"Professional workers join service workers as being significantly more likely to report having depression than the six groups least likely to be depressed, including managers/executives. Depression rates among nurses, physicians and teachers are similar to those found among professional workers and service workers."

The good news is that the rates reported for all categories examined were lower than the national average.

"Regardless of occupational category, depression rates are low, with well over nine in 10 workers in every category saying they are not currently depressed or being treated for depression," Gallup concluded.