Work can be challenging. There are days we walk in with enthusiasm, and days we dread that don't seem to end. It's hard to say which career is the hardest, but there are jobs that are more taxing on employees, at least when it comes to mental health.

In a recent study published in Environmental Health, researchers found commercial airline pilots show higher depression symptoms and suicidal thoughts.

“We found that many pilots currently flying are managing depressive symptoms, and it may be that they are not seeking treatment due to the fear of negative career impacts,” said Joseph Allen, study author, and an assistant professor of exposure assessment science, in a statement.

Read: Women With Top Jobs Often Face Depression

The study comes amid the March 2015 murder-suicide crash by a pilot for the European airline Germanwings. This prompted researchers at the Harvard Chan School to find out how many pilots struggle with depression and suicidal thoughts.

Male pilots were more likely than female pilots to report experiencing loss of interest, feeling like a failure, and thinking they would be better off dead, on a daily basis. Female pilots were more likely than male pilots to have been diagnosed with depression. Pilots taking sleep medications, and those who were experiencing sexual or verbal harassment, exhibited higher depression symptoms.

Out of 1,850 commercial airline pilots surveyed from 50 countries, 13 percent met the criteria for depression, and slightly over four percent had suicidal thoughts over the past two weeks.

The survey asked questions about job content and health from the Job Content Questionnaire (JCQ) and the U.S. Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES), including questions about mental health doctors use to diagnose depression.

The researchers designed the survey with a mix of questions so it would appear to be less obvious about mental health. This strategy was employed to minimize potential bias in responses.

"Our study hints at the prevalence of depression among pilots — a group of professionals that is responsible for thousands of lives every day — and underscores the importance of accurately assessing pilots' mental health and increasing support for preventative treatment," said Alex Wu, first author of the study, and a doctoral student at Harvard Chan School.

The Federal Aviation Administration, which oversees airline safety, has grounded pilots who admitted they were depressed or were taking antidepressants. However, other research has shown those who suffer from depression were either not getting treatment, or were taking antidepressants without reporting those medications to Aviation Medical Examiners, who must clear them to fly. In 2010, the FAA announced that pilots with mild-to-moderate depression could continue flying if they were taking one of four approved antidepressants for 12 months with satisfactory results.

Read: Constantly Sitting Down Could Worsen Anxiety And Mental Health

The airline industry is not the only occupation with high rates of depression.

A 2014 study highlighted the type of profession in which we work can be a risk factor for depression. People who work in public transit, real estate, or social work were more likely to develop depression. These industries require frequent or difficult interactions with the public or clients, and have high levels of stress and low levels of physical activity that tend to be most susceptible to depression symptoms.

1. Local/Intercity Passenger Transit — 16.19 percent

2. Real Estate — 15.65 percent

3. Social Services — 14.60 percent

4. Miscellaneous Manufacturing Industries — 14.25 percent

5. Personal Services — 14.25 percent

6. Legal Services — 13.44 percent

7. Environmental Quality/Housing — 13.42 percent

8. Membership Organizations — 13.28 percent

9. Security and Commodity Brokers — 12.60 percent

10. Printing and Publishing — 12.43 percent

Researchers obtained insurance claims data for 214,000 people in western Pennsylvania employed across 55 industries. The stats are primarily based on a sample of western Pennsylvania, so we can't generalize trends in this region to the U.S., nor the world. For example, coal mining was linked with the highest risk for suicide in a study of British workers, "but in Western Pennsylvania, coal miners had amongst the lowest rates of treated depression.”

Meanwhile, transit workers, such as bus drivers, do face significant rates of depression. A 2006 paper, documenting 50 years' worth of studies on bus drivers and depression, found surprisingly similar characteristics. Bus drivers had among the highest levels of depression, and felt physically and mentally depleted.

The normal wear-and-tear of life can make anyone exhausted; our jobs could affect it to for better or for worse.

Source: Wu AC, Donnelly-McLay D, Weisskopf MG et al. Airplane pilot mental health and suicidal thoughts: a cross-sectional descriptive study via anonymous web-based survey. Environmental Health. 2016.

See Also:

Anxiety vs. Depression: How They Differ And What To Do

Online Insomnia Therapy May Help Ease Depression Symptoms