Rapid cycling bipolar disorder is traditionally defined as four or more episodes occurring within a 12-month period. However, this only applies to the previous 12-month period and does not take into account whether or not a person experiences rapid-cycling only briefly or over a lifetime. A new study has shown that there are several differences between groups that experience traditionally-defined rapid cycling and those who have a lifetime definition of rapid-cycling.
It is not known how many people with bipolar disorder experience rapid cycling. Previous estimates have shown anywhere from 20%-84%. It is more common in bipolar II and may be more common in women. People with rapid cycling tend not to respond as well to treatment.
There are at least two ways to define rapid-cycling in bipolar disorder. The first is set by the diagnostic tool Diagnostic and Statistical Manual of Mental Disorders (DSM). It states that a person with either bipolar I or bipolar II must experience at least four mood episodes in the previous 12 months.
Another definition, the lifetime definition, is considered a more real-world definition that does not necessarily stick to the DSM definition to the letter. Instead of looking only at the previous 12 months, it takes into account an average of at least four episodes per year over a lifetime. Most people only experience rapid cycling for short periods of time, so this would apply more to people with chronic rapid-cycling.
The mood swings in rapid cycling bipolar disorder do not have to follow a particular pattern, they simply have to qualify as either a manic/hypomanic or depressive episode. People with bipolar II do not experience full manic episodes, so their rapid-cycling would only involve hypomania and depression. If there are two episodes of the same type sequentially (depression followed by depression), there generally has to be a period of two-months between the episodes in order to qualify as two separate episodes.
An article published in the journal Bipolar Disorders with research by Jay D Amsterdam and his team at the University of Pennsylvania looked at the differences in treatment outcomes of 129 currently depressed bipolar II patients, 57 of which had not experienced rapid cycling. They looked at which definition participants fell under as well as how they responded to treatment over a period of either 12 weeks or 36 weeks, depending how well they responded to treatment. Approximately 43% of the participants met the DSM requirement for rapid cycling. Approximately 47% met the lifetime definition and 34% met requirements for both.
Here is what they found:
- Those with the lifetime definition tended to have more of a history of depressive episodes compared to hypomanic.
- Those who met the traditional and/or both definitions tended to have a younger age of onset of hypomania.
- That same set had shorter periods of depression compared to those who only qualified for the lifetime definition.
- Participants with the DSM definition of rapid cycling tended to have a higher baseline for hypomanic symptoms.
- The lifetime definition was better at predicting subsyndromal hypomania.
When participants were treated with either venlafaxine (Effexor) or lithium, they found the following:
- There was no significant difference in response rates between the groups.
- Venlafaxine had a response rate of 67.7% whereas lithium had a response rate of 34.4%.
- Relapse rates were similar between groups after initial treatment.
- Rates of treatment-emergent hypomania were similar between groups treated with venlafaxine and lithium.
It should be noted that the use of antidepressants such as venlafaxine in people with bipolar disorder is generally contraindicated as they can induce mania or hypomania, especially when not used along with a mood stabilizer.
Knowing which definition a bipolar II patient falls under may not predict treatment response (specifically with venlafaxine or lithium) but using both definitions of rapid cycling instead of just the DSM definition may be helpful, especially when a patient experiences longer and more frequent depressive episodes.
Image credit: Tessa Sheremeta