Some of these happiness habits may surprise you, but scientific research shows they really work.

1.  Smell the roses.  Harvard research found that people who kept freshly cut flowers in their home for a week reported feeling more energized and less anxious.

2.  Spend wisely.  In a 2014 study, San Francisco State University researchers discovered that splurging on life experiences (like a weekend trip) made people happier than purchasing material items.

3.  Consider a D supplement.  A 2012 study of more than 12,000 people found that those with the lowest levels of vitamin D were the most likely to be depressed.  Talk to your doctor about getting a blood test to see if you're deficient.

4.  Work out regularly.  Starting a fitness routine that includes three sweat sessions a week could reduce one's risk of depression by about 16 percent, suggested British research published in 2014.