The premier of season 2 of Showtime's mega-hit series "Billions" was released last week to much anticipation.

But amidst the high-octane drama lies an extremely important -- but perhaps overlooked -- business lesson that every leader should understand. Before we get to that, however, let's take a step back. If you're not familiar with the show, let me give you a (very) brief recap:

Damian Lewis' character runs a very wealthy and powerful hedge fund, which consistently outperforms its competition. Believe it or not, the company actually employs a full-time, in-house behavioral therapist and psychologist who looks after the mental health of the organization.

This unique addition gives the staff a 24/7 outlet to vent their frustrations, encourage their abilities and ensure peak performance at all times, which really pushes the company one step ahead of its competition.

Leaders everywhere take note: the mental capacity of your staff has a direct correlation to performance and results.

We've reached out to leading influencers across a number of different fields and industries to add a bit of extra weight to our analysis. So without further ado, here's a look at the number one unexpected, powerful business lesson we can learn from watching Billions.

A Changing Landscape

There's no denying that companies have made massive shifts in terms of benefits, employee engagement and office layouts over the past decade. But slides, bean bags and nap pods aside, there seems to be one element that's missing: our mental health. Think about it. Many big organizations now boast on-site gyms. This makes sense, because when you look after your body, you also look after your work performance (not to mention it's a great time-saver).

But to be really sharp and stay on top of your game mentally, how great would it be if your company employed a full-time psychologist - on site. Think about the time you nearly had a nervous breakdown before that big pitch, or that quick-sand feeling we get when we're stressed and can't seem to pull ourselves out.

All of these situations (and many more) have a dramatic impact on employee engagement, satisfaction, performance, and ultimately - ROI.

The Scientific Case for Mental Health

Studies on mental health issues in the workplace suggest time and again that the financial cost to companies could be eased if employees in need received proper treatment. Let's be clear: "mental health" issues can apply to a range of disorders. Generalized anxiety disorders, depression, stress, ADHD and many others are commonplace in our society, but often seem to be pushed under the table at work. Why is this? Are we afraid of being honest with others about our struggles for fear of consequence?

A Harvard study from 2010 found that the indirect costs of mental health (loss of hours, performance, etc.) exceeded companies spending on direct costs (health insurance and pharmacy expenses). But rather than try to treat the symptoms with an expensive array of pills, what if more companies took the Billions approach and hired an on-site psychologist?

A Word From The Experts

To understand more about the importance of mental health at the workplace, we reached out to three experts, each of whom brings a different perspective to improve performance and well-being at the workplace.

Lee Grant, Co-Owner and Clinical Director at Efficacy

Lee echoes the importance of emotional well-being in the workforce, not just for employee happiness, but also for productivity and ROI. "Our performance is a result of a complex active interaction between thoughts, feelings and behaviors. Managed well, we demonstrate our resilience. When not, there is a fine tipping point into underperformance, presenteeism and absenteeism."

Lee continues, "For employees currently performing well, employers could provide specific programs to enhance resilience. For example, Executive Health Programs (EHP) check emotional buffers, stop signals, work-life balance and examine stress responses. On a broader offering, to rejuvenate a team, at least 30% of the working population would benefit from a 2-hour 'Lunch and Learn' on managing sleep."

Charlotte Marshall, VP, Digital Media & Employer Brand at Magellan Health

"Magellan's roots began in behavioral health management, so we're lucky enough to enjoy a number of really great benefits when it comes to physical and emotional well-being at the workplace. Work and life are no longer separate, and many of our employees now work 'virtually,' so they can manage their own lives in a way that's healthy and beneficial for both work and personal commitments. Digital platforms can help facilitate this flexibility, so you really need to harness the tools at your disposal. At Magellan, for example, we have access to our ground-breaking computerized cognitive therapy sessions for behavioral health concerns, in addition to core Employee Assistance Program benefits. Above all, our business is focused on guiding humanity to live healthy, vibrant lives -- and our employees are no exception."

Michael Gilmore, Co-Founder at Mettaflow

Mettaflow is at the forefront of exploring human potential in the workplace. "When you're in a Flow state, time seems to slow down and you're able to perform faster, better and more efficiently. One of the great benefits of Flow lies in its ability to unite teams to work towards one common goal. Ask yourself: what is one of the most optimally performing teams on the planet? The U.S. Navy Seals. And yes, they are one of the world's biggest investors into Flow research. So if you're looking to give your business that extra competitive edge, then Flow is one area you absolutely must explore."