Enlisted military personnel and those working in the emergency services field are under the most stress.

Not all stress is bad. Healthy stress can serve as a motivator, while unhealthy stress zaps concentration.

More than half of Americans report that work is a significant source of stress in their lives. The least stressful jobs include diagnostic medical sonographer, compliance officer and hairstylist.

It may come as no surprise that careers in the military and public safety sector are considered among the most stressful jobs. For the third year in a row, enlisted military personnel, firefighter, airline pilot and police officer are the four most stressful occupations, according to CareerCast's annual Most Stressful Jobs report.

Kyle Kensing, online content editor for CareerCast, said the specific factors his company uses to measure the stress level of an occupation were the most prevalent in military service, police work and firefighting more than any other career. [See Related Story: Entrepreneurs Share Their Stress-Busting Secrets]

"These [factors] include physical demands, on-the-job hazards, environmental conditions, [and] the risk of personal injury or injury to another for whom the worker is directly responsible," Kensing said.

This year's 10 most stressful jobs and their stress scores are

Enlisted military personnel: 72.58 Firefighter: 72.38 Airline pilot: 61.20 Police officer: 51.94 Broadcaster: 51.27 Event coordinator: 51.19 Newspaper reporter: 49.96 Public relations executive: 49.48 Senior corporate executive: 48.97 Taxi driver: 48.17

The average salaries of high-stress jobs that pay well include

Surgeons: $208,000 Lawyers: $119,250 Airline pilots: $121,408

It's not just the inherent, high-risk nature of some jobs that are to blame for high levels of stress and burnout. There are other reasons why someone might be biting their nails at work.

Overall, CareerCast's ranking system considered 11 job demands that evoke stress. These factors included

The amount of travel Growth potential Deadlines Working in the public eye Competitiveness Physical demands Environmental conditions Hazards encountered Risk to one's own life Risk to the life of another person Meeting the public

Although newspaper reporters or broadcasters do not face the physical dangers that police officers or firefighters do, these individuals face strict, constant deadlines. Further, those working in the news industry deal with the fear of lawsuits and a dwindling job market, which also contribute to high stress levels.

Kensing said that many of the most stressful occupations share a common factor – they are crucial to safety and democracy in the U.S.

"Firefighters, military and police officers protect us, and newspaper reporters and broadcasters have a big impact in showing us the truth amidst the trend of 'fake news,'" he said.

For 61% of Americans, the workplace is a "significant" source of stress, according to an American Psychological Association survey. Four of the biggest contributors – micromanaging supervisors, uncommunicative bosses, constant distractions and zero potential for a higher salary or position – stymie productivity and gut employee morale, and the effects spill over into other areas of work and employees' personal lives.

When every decision and email is vetted by a supervisor before any move can be made, it wastes a lot of time, especially when quality work can be achieved without constant check-ins. For a new hire, increased monitoring may be necessary for the first few months of their employment, but when it becomes part of the work culture, it can injure the morale of employees.

"Lack of freedom around decisions can make you feel restricted when it comes to your autonomy," said Marni Amsellem, a licensed psychologist who started Smart Health Psychology, a health psychology consulting business. "When [employees] feel overmanaged, it … undermines their value and what they're able to contribute, and that is going to create tension."

For some, being "in the zone" and completing assignments back to back feels good. However, little things like answering a text message or chatting with a co-worker interrupt productivity, which can put you behind, which increases your level of stress.

Keeping interruptions to a minimum creates more time for you to stay focused and on top of your workload.

A boss who doesn't provide you with any feedback – good or bad – can cause you to worry if you're doing a good job. And that constant worry can put a sizable dent in productivity.

Having clear and open communication on both sides can eliminate confusion and any concerns. If your boss, though, isn't one to share feedback with you, checking in with him or her and asking questions about how you're doing and where you can improve can help put your mind at ease.

Having a job that doesn't pay well is stressful for a number of reasons. Not only is there the constant strain of not meeting your financial responsibilities, but jobs with low salaries and or no room for advancement cause workers to feel undervalued, hopeless and depressed.

According to a study published in the journal of Social Psychiatry and Psychiatric Epidemiology, bus drivers have the highest rates of depression (16.2%) followed by real estate agents (15.5%) and social workers (14.8%).

Not all stress is negative; the truth is, it's a spectrum. Healthy stress can motivate you to finish daily tasks and meet goals, said Amsellem. However, unhealthy stress leads to a host of problems.

When anxiety dominates your daily thoughts, that's a sign that the level of stress you're dealing with is harmful to your health. Chronic stress is associated with

High blood pressure

Weakened immune function

Heartburn

Insomnia or tiredness

Weight gain

Missed periods

Erectile dysfunction

Head and stomach aches

Trouble concentrating

Irritability

Burnout – mental, emotional and physical exhaustion ‒ is the culmination of trying to manage stress for too long. Any job where you're dealing with people puts you in jeopardy of burnout. Emergency service workers are especially vulnerable. In a Medscape survey of 15,000 American doctors, 44% reported feeling burned out.

If you have a high level of stress from your job, finding productive ways how you can deal with it depends in large part on the nature of your job, Kensing said.

"If you work as an airline pilot, spending long stretches packed onto an airplane," said Kensing, "a vigorous exercise routine is more fitting than if your stress comes from physical demands, as is the case for a firefighter."

These other three recommendations can help you tame out of control stress.

Nothing's more frustrating than an unfinished to-do list, but sometimes it's not us, it's the list. For your next assigned project, rather than add the entire project to your to-do list, consider the scope of the project, then prioritize the most critical elements of the project and divide those elements into small, manageable assignments that can reasonably be completed at the end of each day. Using this strategy can help you turn in projects that are on time, error-free, and you won't be completely frazzled when it's done.

Today, it's easy for work to follow you home. Our phones can keep us chained to the office if we don't set clear boundaries. If an email or phone call comes in during the ride home, try not to answer it. Taking your work email off your phone or having a designated phone for work that you can turn off at the end of the day gives you a chance to recharge, giving you the energy and focus you need when it's time to focus on work.

Stress is a fact of life, and while we can't eliminate stress, we have control over how we respond. Avoid unhealthy coping strategies like turning to junk food or alcohol to quell anxiety. Exercise or do whatever relaxes you, whether that is solving a crossword puzzle or spending time with your family and friends. If venting about work to someone helps you feel better, do that. The key is to engage in healthy activities that bring you peace; explore outlets that are "social, physical or creative," suggests Amsellem.

"No matter your profession [though], speaking with a healthcare professional can be a critical stress reliever," Kensing said.

According to CareerCast's study, a diagnostic medical sonographer is the least stressful job. The median income is $71,410 and the projected growth rate of the profession is 23%.

Here are this year's least stressful jobs and their stress scores:

Diagnostic medical sonographer: 5.07 Compliance officer: 5.76 Hairstylist: 6.72 Audiologist: 7.28 University professor (tenured): 8.42 Medical records technician: 8.52 Jeweler: 9 Operations research analyst: 9.09 Pharmacy technician: 9.19 Massage therapist: 10:39

However, just because these jobs correspond with the lowest levels of stress doesn't mean that individuals in these professions don't have stress, Kensing said.

"All fields have their stresses," Kensing said. "It may come from the expectations placed on you by a client, employer or yourself. The nature of our stresses vary."

You can find more details on the methodology CareerCast used to determine its rankings here.