What is the Difference Between Bipolar I and Bipolar II Disorder?

The severity of mania varies between the bipolar types

BP I and II Difference?
© 2014 Marcia Purse

Bipolar disorder is a mental health condition defined by periods (better known as episodes) of extreme mood disturbances. While you may have known this fact, you may not have known that there are two types of bipolar disorder: 

  • Bipolar I disorder
  • Bipolar II disorder

According to the Diagnostic and Statistical Manual of Mental Disorders, published by the American Psychiatric Association, if you have bipolar I disorder, you have episodes of mania and depression.

If you have bipolar II disorder, you have episodes of depression, as well as a less severe form of mania called hypomania.

A Prominent Difference: Hypomania Versus Mania

The main difference between the two types of bipolar disorder is that a person with bipolar I has manic episodes, while someone with bipolar II has hypomanic episodes. So, in other words, it's the severity of the mania that distinguishes these two types.

Hypomania in Bipolar II Disorder

In the hypomania of bipolar II disorder, a person has a sustained mood that is elevated (heightened), expansive (grand, superior), or irritable. This mood has to be noticeably different from his or her normal mood when not depressed. 

Examples of hypomanic symptoms include:

  • Not needing a lot of sleep, but not being tired
  • Having more energy than usual
  • Risky behavior, such as reckless spending
  • Grandiosity, pressured speech and/or racing thoughts.

For example, Hank, when he has hypomanic episodes, is exceptionally cheerful, needs only three hours sleep instead of his usual seven, spends more money than he should, and speaks far more rapidly than usual.

While there are cheerful people who need little sleep, spend a lot, and talk fast who don't have bipolar disorder, this behavior is noticeably different from his own stable mood. So while it's abnormal for Hank, it's not outside the range of possible behavior in general.

It's also important to note that hypomania may interfere to a degree with daily functioning, but not severely.

For example, Hank may be longing to take flying lessons while hypomanic, but if he does, he takes them at a reasonable time when he has no other obligations.

Also, an episode of hypomania does not escalate to a point that a person needs hospitalization, which may happen with a person experiencing mania—especially if he or she is becoming a danger to others and/or themselves. 

Mania in Bipolar I Disorder

In mania, a person's mood is extremely abnormal and is also combined with increased activity or energy that is also abnormal.

For instance, Hank's friend Robert, who has manic episodes, is out-of-control happy, even during serious events (he once burst out laughing disruptively during a funeral). One time, he ran around outside at midnight shouting how much he loved all his neighbors. This is abnormal behavior for anyone.

Unlike hypomania, the day-to-day life of a person with mania is significantly impaired. For example, Robert missed an important business meeting because of a spur-of-the-moment decision to take flying lessons. 

In addition, mania may include psychotic symptoms—delusions or hallucinations—but hypomania does not. For example, at times Robert firmly believes he is the mayor of his town and introduces himself to people as such, telling them about grandiose and sometimes bizarre plans he has for making improvements to services and infrastructure.

Two Caveats When Diagnosing the Type of Bipolar Disorder

There are two important caveats that may further complicate the process of distinguishing the two types of bipolar disorder.

One is that although present psychotic symptoms are one of the things that differentiate bipolar I mania from bipolar II hypomania, someone with bipolar II may experience hallucinations or delusions during depressive episodes without the diagnosis changing to bipolar I.

The second is that someone with bipolar I disorder may also have hypomanic episodes. In fact, they commonly do. But, someone with bipolar II does not ever have a manic episode.

If a manic episode occurs in someone with bipolar II, the diagnosis will be changed.

Similarities Between Bipolar I and Bipolar II Disorder

Despite the major difference when it comes to mania in the two types of bipolar disorder, there are quite a few similarities.

For one, to diagnose bipolar II disorder, one or more major depressive episodes must occur. In bipolar I disorder, a major depressive episode (one or more) usually occurs, but it is not required. 

Common symptoms that occur in a major depressive episode include:

  • Insomnia or hypersomnia
  • Unexplained or uncontrollable crying
  • Severe fatigue
  • Loss of interest in things the patient enjoys during euthymia
  • Recurring thoughts of death or suicide

Secondly, in both disorders, there is a middle ground as well, called euthymia—a symptom-free or "normal" state.

Lastly, for purposes of diagnosing bipolar disorder (regardless of the type), a person's mood symptoms cannot be better accounted for by another psychotic illness like schizoaffective disorderschizophrenia, delusional disorder, or schizophreniform disorder.

Both Types of Bipolar Disorder are Disabling

Since hypomania is less severe than the mania that occurs in Bipolar I disorder, Bipolar II is often described as "milder" than Bipolar I—but this is really not true. Certainly, people with Bipolar I can have more serious symptoms during mania, but hypomania is still a serious condition that can have life-changing consequences.

In addition, research suggests that Bipolar II disorder is dominated by longer and more severe episodes of depression. In fact, over time, people with Bipolar II become less likely to return to fully normal functioning between episodes.

One study specifically concluded that bipolar type II was linked to a poorer health-related quality of life compared to type I—this remained true even during long periods of euthymia.

Thus, experts tend to believe that Bipolar II disorder is equally (if not more) disabling as Bipolar I disorder because they are ill more often, have more lifetime days spent depressed, and don't do as well overall between episodes.

A Word From Verywell

Bipolar disorder is a complex mood disorder. If you are worried that you or a loved one has symptoms of bipolar episode, please seek out medical attention for a proper psychiatric evaluation. The good news is that with the right medication and support, this chronic mental health condition can be managed. 

Sources:

American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5).

LaBouff L. (2016). How Bipolar II is DifferentPsych Central.

Maina G et al. Health-related quality of life in euthymic bipolar disorder patients: differences between bipolar I and II subtypes. J Clin Psychiatry. 2007 Feb;68(2):207-12.

Swartz HA, Thase ME. Pharmacotherapy for the treatment of acute bipolar II depression: current evidence. J Clin Psychiatry. 2011 Mar;72(2):356-66.

U. S. Department of Health and Human Services, (April 2016). National Institute of Mental Health: Bipolar Disorder.

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