There are many reasons why a person can experience mood swings. They often involve many biological systems and, as such, the research around them is complex and ongoing.

"Mood swings are significant changes in mood," said Dr. Elizabeth Wassenaar, regional medical director of the Pathlight Mood & Anxiety Center in Colorado. "While we mostly think of shifting from happy to sad, mood swings can also include shifting from being calm to anxious or from feeling unbothered to irritable."

Mood changes are a natural part of the human experience. Yet if symptoms are extreme or interfere with a person's daily life, it may indicate an underlying cause.

"Anyone can experience occasional mood swings, and in certain times of our lives, they are more common," Wassenaar told Live Science, including during life changes such as puberty, pregnancy, menopause, and during periods of high stress and poor sleep.

So what causes mood swings? Many interacting elements influence mood, including psychological and social factors, lifestyle and underlying physiological changes. Here are some of the common causes.

Mental health disorders