After Mariah Carey's diagnosis: What is bipolar II disorder?

After suffering in silence for nearly two decades with bipolar disorder, Mariah Carey reveals in this week's People magazine cover story that until recently seeking treatment, she lived in fear of someone finding out about her diagnosis. The disorder, which can cause unusual mood shifts and affect energy and activity levels, is characterized by swings from very "up" moods that are elated and manic to "down" periods marked by hopelessness and depression.

Carey says she was first diagnosed with bipolar disorder II in 2001 and is now in therapy and taking medication, which seems to have stabilized her condition. Carey told the magazine she was "in denial" about her diagnosis 17 years ago but realizes now that "it does not have to define you and I refuse to allow it to define me or control me." Billboard reached out to UPenn Perelman School of Medicine professor of psychiatry Michael Thase to find out more about the the impact and treatments for bipolar disorder.

First things first, Thase explained that there is a big difference between the more severe bipolar I disorder versus the type Carey says she has. "The classic form of manic depression is what's called bipolar I disorder, where there would be periods of depression and abnormal elation -- that's where the mania is," Thase tells Billboard about frantic periods where patients may not sleep for days, or weeks, as they seek out stimulus or plow their energy into multiple, ambitious tasks. "Take a peak experience and sustain it over days or weeks where you don't have a need to sleep, you feel more talented, smarter and more productive and sometimes you can even become convinced about things that are not true, like you have the secret to world peace."

Thase -- who has not treated Carey and has no firsthand knowledge of her case but was speaking in more general terms about the disorder -- adds that those suffering from bipolar I disorder can also develop delusions of grandeur. By contrast, he describes bipolar II as something between recurrent depression and classic manic depression, where there may be abnormal elation for a period that doesn't rise to the level of mania or involve a psychotic episode that requires hospitalization, as well as periods marked by depression. "You might be more irritable or headstrong, do things your trusted advisers might think are beyond your abilities," he says.

Though there is no known definitive cause for bipolar disorders -- which are considered to affect the patient for their lifetime -- doctors believe it might be a result of either environment or genetics, or both. Another dangerous factor is the possibility that a patient may have a higher risk of developing other disorders, including addictions to legal or illegal substances. "Anytime you hear about a celebrity who becomes 'exhausted' ... three or four weeks is the typical amount of time needed to recover from a manic episode," he says, noting that it's possible that someone might self-medicate as they seek to balance their wild mood swings.

The manic episodes in bipolar II sufferers can be disruptive and are often characterized by rapid, disorganized speech, long stretches of sleeplessness and unpredictable mood swings that can make completing professional tasks difficult, if not impossible as the patient moves unpredictably from enthusiasm to lethargy. Extreme stress, sleep disruption and drugs or alcohol can also trigger episodes in patients vulnerable to bipolar II.

Compared to 20 years ago, Thase says the stigma around bipolar disorder is much lower today, noting that 12 percent of the population suffer from a level of depression that should be treated, with half falling squarely into the sphere of the bipolar spectrum and one percent of that 12 percent susceptible to manic episodes. "That means if you're in a room with 50 people, one of them likely has bipolar disorder," he says, with the American Psychiatric Association noting that 80-90 percent of sufferers having a relative with either depression or bipolar disorder. "They're not rare conditions and if treated well and detected early -- and you don't get into other trouble, it's easy to pick up drug and alcohol issues during these manic periods -- they are easy to pick up and treat. It's nothing to be ashamed about."

About two-thirds of bipolar cases can be treated fairly easily, according to Thase, with those that are more challenging often manageable through a combination of treatment by a trained therapist and more aggressive strategies. The good news for Carey is that there are proven treatments that most patients benefit from, including the mood stabilizer Lithium, as well as alternatives such as the anticonvulsants Depakote and Tegretol and newer anti-psychotic drugs such as Seroquel. The downside is that drugs such as Lithium come with side effects such as tiredness and sluggishness, as well as weight gain.

Doctors also recommend getting regular sleep and maintaining a healthy, balanced diet in order to help

"Sixty years ago we thought we couldn't treat manic individuals because they were too in their head and they couldn't focus, but modern psychiatry has proven very useful," says Thase.