Earlier this year, burnout was added to the World Health Organization's list of official medical diagnoses . Burnoutcanoccur when we face chronic work stress, explained David Ballard, senior director of the American Psychological Association's Office of Applied Psychology. We are really only equipped to handle stress in short bursts -- so when we face elevated levels of stress at work for a long time, we risk burning out.

"If it's not managed effectively over time, it can affect job performance," said Ballard. "It can leave one feeling exhausted, unmotivated and ineffective on the job. Job performance can also suffer."

Managers and employees both play a role when it comes to identifying and managing burnout.

"Employees have to take steps to have effective coping skills to manage stress," said Ballard. "Employers can work to create an environment that is conducive to healthy employees: identifying stressors and reducing and eliminating them when they can and making sure they have health and management resources."

Here are some potential red flags that managers can look for:

First in, last out

There are going to be times when work requires long hours -- but you can only burn the candle at both ends for so long.

"Pushing yourself for a few weeks is okay ... but after a while it becomes really detrimental to your health and ability to do work at the same quality level," said Leigh Stringer, author of "The Healthy Workplace."

Managers need to set the tone when it comes to work-life balance. Don't be afraid to stress the importance of having a life: ask about outside-of-work activities, offer flexible work arrangements to help navigate busy schedules, and exhibit the behavior you want to see.

"The key is communicating expectations," Ballard said. "If you are in a senior leadership position and are putting in long hours into the evenings and weekends and that fits well for you, make sure you are clear with your employees what is expected of them."

Everything is a priority

Workers who might be struggling with burnout could have a hard time prioritizing tasks.

"When somebody sees everything as being a really high priority, they don't know what to minimize and they don't know when to stop," said Adam Goodman, director of the Center for Leadership at Northwestern University.

When giving a new task or project, managers should ask employees what else they have going on to make sure no one's plate is getting too full and to help prioritize assignments.

There's silence

When a typically chatty employee who often participates in meetings and is engaged and enthusiastic suddenly becomes unmotivated and quieter, that person could be at risk for burnout.

"Their bodies are at work, but their heart and soul are not, and you are noticing a lower participation rate," said Stringer.

How they describe their work can also be telling.

"If you ask how a project is going and normally they give you a full lowdown, and instead they're now giving one-word answers ... and seem completely disengaged with it, that is a sign a team member may experience burnout," said Ben Fanning, author of "The Quit Alternative: The Blueprint for Creating the Job You Love Without Quitting."

If you are sensing some distance from an employee, try pulling them aside and asking them to grab coffee or go for a walk. "Take them outside the throes of work and have an off-site discussion that shows you care about them as a person. Reaching out is very important," said Stringer.

A sour apple all the time

Venting in the workplace is common — and sometimes helpful. But when a person becomes overly negative all the time without offering solutions, it could be a sign they are stuck in a rut, according to Fanning.

Also pay attention to any shifts in behavior.

For instance, if an employee is normally very cordial and patient with coworkers or customers, but is now frequently losing patience quickly, that can also be a sign of burnout, Fanning added.

Negative attitudes are contagious and can spread throughout an office and take a toll on productivity and engagement.

Fanning suggested taking a "set, achieve and celebrate" tactic in the office. This involves setting clear goals and once they are achieved, celebrating them. "A lot of managers don't set a clear goal, they just want to achieve," he said. And when it comes to celebrating, it doesn't have to be a big office party. "Recognize the work or person in a team meeting. A little bit of recognition can really help out."

Cognitive Issues

We all make mistakes. But when they become repetitive it may signal a problem.

"If they keep making the same mistake frequently and they aren't in the zone, that could be a sign of experiencing burnout," said Fanning.

Other red flags are when people start having difficulty with concentration and have a harder time solving problems and issues with memory or making decisions, according to Ballard.

"If someone's is work performance is slipping, it gives you the opportunity as manager to have a conversation and point to resources to help support," he said.