Bipolar disorder, the most extreme form of which was previously known as manic depression, is a significant disturbance of mood characterized by 'mood swings', euphoria, high levels of energy and productivity. It is possibly the only condition where sufferers actually crave the return of some of the symptoms and it remains one of the most intriguing and disabling psychiatric disorders. Individuals with the disorder have demonstrated remarkable levels of creativity in fields such as literature, visual arts, music and history.
The disorder was described as early 1921 by Kraepelin who noted the range of symptoms, pattern of episodes and impairments in functioning. The disorder can have a lifetime prevalence of up to 2% (depending on the type of criteria being used) with many suffering from recurrent multiple and disabling episodes despite the use of mood-stabilizing medicines. Although bipolar disorder can (rarely) persist in childhood, onset is commoner in the teens or early 20s. One epidemiological study has suggested a rate of 1% among adolescents (Lewinsohn, Klein and Seeley, 1995).
The disorder is associated with high mortality and morbidity rates. Lifetime risk for suicide for people with bipolar disorder is 15%. Around one quarter of people with bipolar disorder will make a suicide attempt (usually related to the depressive component) sometime in their lives. After cardiovascular events, suicide is the most likely cause of death for individuals with bipolar disorder (Angst et al., 2002).
According to the World Health Organization, bipolar disorder is the sixth leading cause of disability worldwide wide (measured in DALYs – disability adjusted life years). The burden of living with bipolar disorder is immense in terms of lost productivity and social relationships, not only to the individual but also to families and communities in general (for example, in one study alone, bipolar disorder was thought to account for 45% of inpatient care costs; Johnson et al., 2003). Up to one third of people diagnosed with bipolar disorder remain unemployed a year after hospitalization for mania (Harrow et al., 1990).
Current conceptualizations of bipolar disorder
There has been considerable debate as to whether unipolar and bipolar disorders are categorical or dimensional constructs. Both the ICD-10 and DSM-IV assert a categorical approach to unipolar and bipolar disorder. However, some studies have argued for continuity between recurrent depressive episodes and bipolar disorder.
There is also debate about the classification of the different types of bipolar disorder. Increasingly however, there has been a move to the development of categories or subtypes of bipolar disorder such as Bipolar I and Bipolar II. The principal types of bipolar disorder, that is Bipolar I and Bipolar II, may be separate sub-types or differ merely dimensionally (eg by severity or duration), with the term 'Bipolar Spectrum' assuming dimensional differences.
The Bipolar Spectrum
I – Manic Depression
II – Depression + Hypomania
III – Hypomania in association with antidepressant medication (starting up, withdrawal). This is referred to as 'switching'.
IV – Depression superimposed on 'hyperthymic temperaments'
V and VI – Other more 'temperament' concepts
From Akiskal (2005), Journal of Affective Disorders, 84, 107-115.
Bipolar I and Bipolar II may be distinguished by a number of key characteristics. People with Bipolar I are more likely to experience more 'severe' and longer highs or manic episodes (which may include psychotic features) and require treatment in hospital than those with Bipolar II. In contrast, Bipolar II is less severe with no psychic experiences, and with episodes waiting to last only hours to a few days. Symptoms of Bipolar II may not be as obvious as those for Bipolar I. While the highs in Bipolar II, often referred to as hypomania, can also be disturbing to sufferers, they are often characterized by periods of intense productivity.
Typically, people can experience a mixture of both highs and lows at the same time, or switch during the day, giving a mixed picture. In rare cases (up to 5%), people with Bipolar Disorder only experience the highs and not the lows. The pattern of the disorder can be quite distinct with some people everyday daily mood swings and others having only one episode of mania per decade. People with bipolar disorder can experience normal moods between their swings.
The popular view holds that Bipolar II is a much milder version of bipolar disorder. However, recent evidence (eg Hadjipavlou et al., 2004) has indicated that Bipolar lI is associated with more chronic and frequent depressive episodes, greater periods of time with sub-syndromal symptoms and higher rates of attempted and completed suicide. Bipolar I and Bipolar II sufferers have equivalent levels of impairments in psychosocial functioning and in use of mental health services. Although the 'highs' in Bipolar II may be less sever than those associated with Bipolar l, the depressive episodes are equally disturbing and debilitating.
The distinction between Bipolar I and Bipolar II has important implications for treatment. In Bipolar I, the mood stabilizers (especially the gold standard, lithium) are considered to be the mainstay of treatment. The role of the mood stabilizers in Bipolar II Disorder is less clear and up for debate, especially as new antidepressants and atypical antipsychotics have come on the market. There is an increasing interest in this area and more trials are currently underway which will hopefully clarify whether each condition should be similarly trated.
In addition, Bipolar I Disorder (but not Bipolar II Disorder) is also characterized by a number of psychotic symptoms such as delusions and hallucinations. These times occur during an acute manic episode but can also occur during a severe episode of melancholic depression. In Bipolar I Disorder, delusions are much more common than hallucinations.
The prevalence of Bipolar II tend to be higher in females and women with bipolar disorder are at a higher risk (around 60%) of having a depressive or manic episode during or (and more commonly) in the first few weeks after delivery. While most will suffer from depression, a significant proportion will have highs, and up to 10% will have mixed highs and lows.