These are 25 of the happiest cities in the U.S., study says

Regular dental checkups and vacation time may not seem related, but according to a survey measuring happiness in U.S. cities, they are both good indicators of overall well-being.

A study compiled by National Geographic, author Dan Buettner and Gallup used 15 factors that also include quality of diet, financial security, and daily learning, among others. The findings are based on 250,000 interviews done across the country from 2014 to 2015 as part of the National Geographic Gallup Special/Blue Zones Index.

Boulder, Colorado toped the list thanks to its proximity to nature, a strong feeling of community, a largely active lifestyle and sustainable development, among other qualities.

Cities from other states included San Diego, Minneapolis-St. Paul, and Washington D.C.

Santa Cruz-Watsonville, California; Charlottesville, Virginia; and San Luis Obispo-Paso, California; were also in the top 5.

Other cities that did not make the list and ranked at the very bottom of the happiness scale were Charleston, West Virginia; Fort Smith, Arkansas; and Hickory-Lenoir-Morganton, North Carolina.

In general, Buettner found that people living in happy cities socialize more during the day, laugh and smile more often, feel financially secure and have access to green spaces.

Here is the full list: