Mariah Carey has bipolar II, but what exactly is that?

Mariah Carey made a surprising announcement on Wednesday: She has bipolar disorder.

Carey, 48, told People that she was first diagnosed in 2001, after being hospitalized for a physical and mental breakdown, and that she has kept her condition a secret ever since. “I didn’t want to believe it,” Carey said of her diagnosis.

In fact, Carey says she only sought treatment for her condition recently, after “the hardest couple of years I’ve been through.”

“Until recently, I lived in denial and isolation and in constant fear someone would expose me,” she said. “It was too heavy a burden to carry, and I simply couldn’t do that anymore. I sought and received treatment, I put positive people around me and I got back to doing what I love — writing songs and making music.”

Carey says she thought for a long time that she had a severe sleep disorder. “But it wasn’t normal insomnia and I wasn’t lying awake counting sheep. I was working and working and working. … I was irritable and in constant fear of letting people down,” she said. “It turns out that I was experiencing a form of mania. Eventually, I would just hit a wall. I guess my depressive episodes were characterized by having very low energy. I would feel so lonely and sad — even guilty that I wasn’t doing what I needed to be doing for my career.”

Carey reveals that she’s now in therapy and taking medication for bipolar II disorder. “I’m actually taking medication that seems to be pretty good. It’s not making me feel too tired or sluggish or anything like that. Finding the proper balance is what is most important,” she said.

As a whole, bipolar disorder (aka manic-depressive illness) is a brain disorder that can cause someone to have unusual shifts in mood, energy, activity levels, and the ability to carry out daily tasks, according to the National Institute of Mental Health. Like many health conditions, bipolar disorder can be broken down into four main categories: bipolar I, bipolar II, cyclothymic disorder, and other types.

Bipolar I causes episodes of mania (i.e. highs) that are preceded or followed by a hypomanic (a less severe version of mania) or depressive episode, the Mayo Clinic says. Bipolar II also causes hypomanic and depressive episodes, but not manic episodes. Cyclothymic disorder is diagnosed when someone has had many periods of hypomania and depression (although less severe than major depression), and “other types” include bipolar and related disorders caused by certain drugs or alcohol, or due to a medical condition, like Cushing’s disease, multiple sclerosis, or stroke, the Mayo Clinic says.

Most people with bipolar disorder are diagnosed as bipolar I or II, Jed Magen, DO, an associate professor and chair of the Department of Psychiatry at Michigan State University, tells Yahoo Lifestyle. The major difference between the two is that people with bipolar I have significant depressions and significant high periods with a lot of euphoria. “They may talk faster, have their thoughts go a million miles a minute, and act impulsively,” he explains. But bipolar II tends to be a “less intense” version of bipolar I, Magen says. “Someone will still have depression and it can be significant, but the up periods are much less high. Often people feel pretty good and on top of the world, but they’re often not so euphoric that they have bad judgment.”

Bipolar II disorder is treated the same way as any other bipolar disorder, which largely involves both medication and psychotherapy, Magen says. With bipolar II disorder, someone may be on a combination of medications like lithium, a mood stabilizer, and antipsychotic medications (it’s not that people with bipolar disorder are psychotic, but the medications can help, Magen says) to help stabilize their mood.

Psychotherapy is also a strong element of treatment, licensed clinical psychologist John Mayer, author of Family Fit: Find Your Balance in Life, tells Yahoo Lifestyle. “It is critical that the therapist administering the psychotherapy is highly skilled with this disorder and, very importantly, is strong enough to direct and monitor the type of psychotherapy necessary to control the illness,” he says. This therapy is very directive, Mayer says. Therapists teach and guide the patient, and intervene in their life to provide structure and boundaries in their behavior, thoughts, and feelings. Mayer adds that the therapy can “work wonders.”

The biggest problem with bipolar II is depression, Magen says, which can be severe. “That’s why it’s absolutely important to seek treatment,” he says. “This is a treatable disorder.”

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