“Uneasy lies the head that wears a crown.” This is the most famous line in William Shakespeare’s play Henry IV, Part 2, spoken by the titular 15th-century English king. He is tired, sick, sad, and alone in his misery. His remark expresses the persistent idea that leaders tend to be isolated and lonely.

Modern research supports this claim. It’s not that leaders are more likely than others to say they are lonely people in general, but isolation and loneliness at work are a special source of unhappiness for people at the top.

Friendship at work is crucial to happiness for most people. According to Gallup, employees who say they have a “best friend” at work are almost twice as likely as others to enjoy their workday. Almost 50 percent more likely to report high social well-being. But people at the top often miss out on workplace friendships, and they may suffer mightily as a result. According to one finding in the Harvard Business Review, half of CEOs experience loneliness on the job, and most of them feel loneliness hinders their work performance. Studies also have shown that loneliness is linked to burnout among leaders.