It's been said that a woman's hair is her best accessory.

When our locks are healthy, shiny and in place just the way we like them, all is right with the world. When they're behaving more like a two-year-old in the grocery store just before nap time, it's another story.

Aside from moments of sheer and utter frustration with the bathroom mirror, the effects of a bad hair day can extend well past morning primping time. In fact, research links bad hair days with entire bad mood days.

Are we really so vain that our hair can affect our whole day?

Yes, says Dr. Marianne LaFrance, Professor of Psychology and of Women's and Gender Studies at Yale University, who analyzed information on how individuals felt during a bad hair day.

According to this study, increases in self-doubt, social insecurities and self-critical thoughts emerged when participants felt their locks were uncooperative. Even job performance was affected.

"Individuals perceive their capabilities to be significantly lower than others when experiencing bad hair," LaFrance stated in the research analysis.

And while both women and men are negatively affected by the phenomenon of bad hair days, LaFrance concluded that women tend to feel more disgraced, embarrassed, ashamed or self-conscious on those days, while men feel more nervous, less confident and less sociable.

Psychotherapist Heather Turgeon is not surprised. "Our culture heavily emphasizes appearance. It affects each person differently, and how we look to the outside world is tied to our mood and self image."

Turgeon says being in a low-confidence-hair-day mood is hard, because you feel like everyone notices, and you're sure that's the first thing they see. "It's kind of a spotlight effect -- you think people are paying way more attention than they really are."

She also says that when we're feeling low we're more likely to think we don't look good, even if our hair looks exactly the same, so a bad hair day is sometimes all in the mind.

"It's probably worse in your head than it is in other people's eyes," says Turgeon. "We think people notice our little gaffes and flaws, but generally they are way more forgiving than we are to ourselves."

Read more on how our hair affects our lives -- and why 27 percent of women would give up chocolate for a lifetime of great hair!