Scientific research shows that being stressed out at work can take a serious toll on your physical and mental health.

In an effort to help people find happiness in the workplace, career and recruiting website CareerBliss recently released its eighth annual list of the 50 happiest companies in America. The distinction recognizes the U.S. companies which are succeeding in building a happier culture and positive work environment for their employees.

The list includes well-known companies including American Express, Apple, Microsoft and Nike, as well as other large and mid-size companies.

For this year's happiest companies list, CareerBliss analyzed data from more than 41,000 independent employee reviews. The CareerBliss board of workplace PhD advisors, which include experts in organizational behavior, psychology and computer science, determined 10 key factors that determine workplace happiness: company culture, growth opportunities, people you work with, person you work for, rewards you receive, support you get, the way you work, work setting, CEO rating and overall company rating.

Reviews are then quantified into what the website calls a "BlissScore" with five being the most positive score and one being the least positive.

"Our data shows that happiness can impact productivity, employee loyalty and overall employee success," CareerBliss CEO Heidi Golledge told CNBC Make It in a statement. "Happiness at work should be one of the first factors we account for when thinking about who we want to work for and how we want to work."

Golledge adds that happiness is a metric which can be used to help employers and employees alike determine the best company for their individual needs.

Here are 25 companies with the happiest employees, along with average salaries and CEO approval ratings, according to CareerBliss:

25. Blue Cross Blue Shield Association

Bliss score: 3.9

Average salary: $47,726

CEO approval rating: 82%



24. American Income Life Insurance Company

Bliss score: 3.99

Average salary: $29,100

CEO approval rating: 73%



23. Fidelity Investments

Bliss score: 3.99

Average salary: $65,000

CEO approval rating: 94%



22. Pfizer

Bliss score: 4.00

Average salary: $81,821

CEO approval rating: 90%

21. Chase

Bliss score: 4.02

Average salary: $51,856

CEO approval rating: 85%



20. Kaiser Permanente

Bliss score: 4.00

Average salary: $80,188

CEO approval rating: 85%



19. Citrix Systems, Inc.

Bliss score: 4.05

Average salary: $126,200

CEO approval rating: 89%



18. The Vanguard Group

Bliss score: 4.06

Average salary: $46,009

CEO approval rating: 91%



17. iGATE Corporation

Bliss score: 4.08

Average salary: $73,818

CEO approval rating: 88%

16. Qualcomm

Bliss score: 4.09

Average salary: $91,187

CEO approval rating: 96%

15. Leidos, Inc.

Bliss score: 4.09

Average salary: $79,903

CEO approval rating: 84%

14. Quicken Loans

Bliss score: 4.11

Average salary: $46,005

CEO approval rating: 100%

13. Apple

Bliss score: 4.18

Average salary: $42,000

CEO approval rating: 92%

12. Starbucks

Bliss score: 4.191

Average salary: $30,000

CEO approval rating: 88%

11. CIGNA

Bliss score: 4.22

Average salary: $78,171

CEO approval rating: 92%

10. TruGreen

Bliss score: 4.23

Average salary: $33,000

CEO approval rating: 75%

9. PNC Financial Services Group, Inc.

Bliss score: 4.23

Average salary: $65,666

CEO approval rating: 100%

8. Bristol-Myers Squibb

Bliss score: 4.23

Average salary: $71,000

CEO approval rating: 67%

7. Intuit, Inc.

Bliss score: 4.26

Average salary: $81,730

CEO approval rating: 96%

6. Chevron Corporation

Bliss score: 4.27

Average salary: $56,000

CEO approval rating: 94%

5. Amgen Inc.

Bliss score: 4.28

Average salary: $75,000

CEO approval rating: 83%

4. Adobe Systems

Bliss score: 4.32

Average salary: $74,008

CEO approval rating: 92%



3. Total Quality Logistics

Bliss score: 4.38

Average salary: $69,142

CEO approval rating: 97%

2. Nike

Bliss score: 4.47

Average salary: $40,000

CEO approval rating: 95%



1. Keller Williams Realty

Bliss score: 4.48

Average salary: $50,000

CEO approval rating: 100%

"It is not necessarily a well-known tech company like Google or Amazon that provides the happiest work environment. Companies need to be able to meet employees' needs across a variety of factors," CareerBliss adviser and University of Tulsa psychology professor Bradley Brummel, PhD, said in a statement.

"We find that employees who have a good relationship with their manager and a positive perception of their CEO are more likely to remain happier at their job and stay with the company longer," he added.



Like this story? Like CNBC Make It on Facebook.

Don't miss: