Imagine you have a friend or loved one whose mood seems to fluctuate as dramatically as a pendulum. He goes through phases in which he's so excited about work projects he stays up all night. The next thing you know, he seems to have lost interest in just about everything.

This is a snapshot of bipolar disorder, which the National Institutes of Mental Health (NIMH) defines as a "brain disorder that causes unusual shifts in mood, energy, activity levels and the ability to carry out daily tasks."

Treating bipolar disorder, which also has been called manic-depressive disorder, can be tricky. One reason is people who suffer from it often are in denial that anything is wrong, according to Barbara Greenberg, PhD, a child and family psychologist in Connecticut and New York. “It’s probably easier to get them help when they’re in a depressive phase,” she adds. “When they’re in a manic phase and elated, they tend to actually like it.”

Related: Teen Mental Health Problems: The Statistics are Eye-Opening

And yet treating bipolar disorder — which usually requires a combination of medication, therapy and family support — is vital.

“People with untreated bipolar disorder can do a lot of damage, leave a trail of wreckage,” Greenberg says. “They behave in ways they ordinarily wouldn’t — for example, spending money they don’t have with credit cards, becoming promiscuous, impulsive or very agitated and angry.”

And they can be suicidal. Fifteen percent to 17 percent of people suffering from bipolar disorder take their own lives as a result of "negative symptoms that come from untreated illness," according to the Treatment Advocacy Center, a national nonprofit organization devoted to timely treatment for mental illness.

Related: Mental Illness in America: Take the Stigma-Free Pledge

Signs and symptoms of bipolar disorder

Given how devastating untreated bipolar disorder can be, it's important to know how to spot it.

“The first sign is dramatic mood swings,” Greenberg says. “The second is the mood swings seem to be unrelated to a trigger in the environment.” She adds that there are two main types of bipolar disorder. “One is where the moods fluctuate quickly. The other is that you’re depressed for months and then you’re manic for months.”

According to the NIMH, these are some typical signs of mania:

  • talking too much and too fast
  • having racing thoughts
  • making impulsive decisions
  • taking risks
  • launching multiple projects
  • sleeping too much or hardly at all
  • over-estimating one's abilities

In a depressive episode, the NIMH says someone with bipolar disorder may:

  • lose interest in most everything
  • feel sad or hopeless
  • become irritable and lash out in anger
  • talk about death or suicide

If you suspect someone you care about is suffering from bipolar disorder, the NIMH says the most important thing you can do is help him get the right diagnosis and treatment, even if you have to call the doctor and go to the appointment with the person you're concerned about.

Then be prepared. According to the Depression and Bipolar Support Alliance (DBSA), just as the illness consists of peaks and valleys, so does treatment. According to the DBSA, recovery takes place when the illness stops interfering with your life.

John McManamy has managed his biopolar illness for years through medication, therapy, yoga, a bipolar support group and writing. “I remember one mixed manic episode,“ John writes on the DBSA website, “that left me jobless and nearly penniless in a far-away country, and the depression that landed me in the emergency room. I know what’s at stake should this illness try to reassert itself. I’m in complete awe of the destructive power of this perfect mental storm. Maybe that’s why I’m still here.”

Related: 6 Things You Shouldn't Do when You're Sleep-Deprived

Like this article? Share it with friends by clicking the Facebook or Twitter button below. And don't forget to visit our Facebook page!

Luke James is a freelance writer and musician who writes about music, soccer, kids, pets and life with his family in northern California.