By Abby Curnow-Chavez for Harvard Business Review

Lately, we have heard a lot from our clients about “toxic” coworkers and teammates. This issue isn’t new; there have been bad coworkers since the beginning of organised work. But these days, their impact feels bigger and more destructive. Businesses need teamwork to function. And teams need to be more collaborative, adaptable, and proactive than ever. The days of top-down decision making are long gone in many companies and industries, as it’s replaced by grassroots innovation that’s unleashed through coworkers openly networking and sharing information across boundaries. Because of this new dynamic, dysfunctional teammates can damage the results of a whole team in a way that was much harder to do in the old, siloed models of working.

The most common and destructive toxic behaviours we see include:

• backstabbing, criticising, and blaming
• gossiping and spreading rumours
• agreeing in meetings, but not following through afterwards
• hoarding information
• purposely undermining others
• caring only about personal agendas (over team and company goals)

We’ve studied thousands of teams and collected data across all industries, sectors, and geographies to learn what makes some teams high performers and what makes others fail. Our research indicates that the single most important factor in team success or failure is the quality of relationships on the team. In fact, 70% of the variance between the lowest-performing teams, which we call saboteur teams, and the highest-performing teams, or what we have labelled loyalist teams, correlates to the quality of team relationships — not some or most of the relationships, but all of them. Thus, one toxic team member is all it takes to destroy a high-performing team.

Toxic team members are destructive because of they:

Create unnecessary drama and distraction. They suck the positive energy and creative brainpower out of the room. Team members waste precious time watching their back, instead of openly innovating, taking risks, and speaking up candidly about what’s on their minds.

Erode the “team brand.” Their bad behaviour poorly represents the team and creates a negative impression with colleagues outside the team. In fact, in our research, stakeholders outside the team are 2,000 times more likely to view loyalist teams as being effective in delivering results, as compared with saboteur teams. It’s clear that team dysfunction is highly correlated with team brand and results.

Undermine the values of the leader and the company. It breeds cynicism when companies espouse the values and norms of behaviour but don’t hold some employees to the same standards.

Degrade the team culture. The saboteur’s behaviour becomes the norm de facto. Well-intended team members begin to reflect this bad behaviour as well, treating a toxic teammate with disrespect, griping behind their back, and keeping them out of the loop whenever possible.

If you are the team leader, the way forward is clear. You need to acknowledge what’s happening with the team, and you must hold the toxic team member to a higher standard of behavior. Regardless of their productivity, results, technical expertise, raw intelligence, or invaluable experience, you cannot tolerate behavior that drags down everyone else on the team.

But what can you do if the toxic person is your peer? Many employees tell us that they feel powerless to change peer behaviour In fact, some end up just leaving the team or company after the impact becomes insufferable to them.

Here are four steps you can take to deal with a toxic coworker:

Have an honest, candid conversation with the person. If you don’t attempt to do this, you are 100% ensuring that the relationship will, at best, continue in its current, dysfunctional state. You cannot assume this person will suddenly wake up and realize the error of their ways, so make an honest attempt to provide productive feedback. Focus on the impact the behavior is having on you. Ask for feedback on your own behavior as well. Sometimes, others don’t realize the impact they are having on you. Research shows that most of us lack self-awareness, especially at work.

Members of loyalist teams are 106 times more likely to give each other feedback than those of saboteur teams, even when it’s tough. Act as a loyalist yourself by opening up an honest, candid dialogue.

Raise your own game, and keep your ego in check. Don’t stoop to their level. Watch for and manage your fight-or-flight response. The more you can maintain your focus on team goals, the less likely you are to become blinded by win/lose thinking with this toxic peer. Be the role model for how you want the team to act. Set a standard with the rest of the team that supports collaboration and open dialogue, not retaliation.

On loyalist teams, team members are 35 times more likely to show a visible commitment to each other’s success, and 47 times more likely to work hard to build and maintain trust, as compared with saboteur teams.

Talk with your boss. Proactively suggest to your boss that the team hold a meeting to set up team norms and begin to address some of the challenging behaviors and conflicts on the team. This session should not be a ruse for taking the toxic team member to task. It should be a real and authentic interaction, in which team members can gain insight into one another’s perspectives, set clear standards of expected behavior, and increase peer-to-peer accountability.

On loyalist teams, team members are 73 times more likely to have a set of norms and behaviors they live by and 125 times more likely to address unacceptable team behaviors promptly.

Finally, take care of yourself. Don’t let this toxic behavior damage your emotional and physical health. Own what you can, let go of what you can’t influence, and make a change if you have to. If you have worked your tail off to develop better relationships with your saboteur coworker(s), and it’s going nowhere, or getting worse, consider seeking the advice of an HR professional or trusted mentor on what else you might try. But if you’ve done everything you can, you should consider leaving. Life is too short for work to suck the life out of you.

When you’re working with a toxic coworker, there is no question that you’re suffering from the experience. And it’s likely that business results are suffering, too. Quite often, the pain provides strong motivation to address the problems and propel things forward, but the work ahead is not easy, and we aren’t going to lie to you: Rebuilding relationships and developing new habits takes a lot of energy and courage. However, once you fully commit to turning around your difficult relationship, you are likely to see improvements. Be well-intentioned in your efforts — and persistent — and you’ll reap the rewards.