Bipolar disorder: Family links to episode frequency

Bipolar disorder –also known as manic depression, is a serious mental illness I've talked about in previous columns.

It is a familial illness characterized by recurrent episodes of mania and depression. There is wide variability in terms of the symptoms presented and the frequency with which the episodes occur. It usually begins in late adolescence or early adulthood but may occur at any age. In general, the episodes become more severe and more frequent over a person's lifetime.

A recent study looked at the frequency of episodes in 407 subjects with bipolar disorder from 86 families. The authors analyzed the recurrence frequency along with associated clinical variables in families who have at least three affected members. They were interested in the extent to which episode frequency is a heritable feature of this condition.

They found that here was a wide variation in frequency of episodes with most people having about 1 episode every 2 years but some having as many as 20 episodes per year. Episode frequency was significantly correlated among relatives and also associated with clinical features such as earlier age of onset, bipolar II disorder, hallucinations and delusions, alcoholism, and suicidal behavior. Most of these are features which are usually thought of as indicating a more severe disorder. The exception to that is bipolar II disorder.

Bipolar disorder is referred to as type I if there is at least one clear manic episode. It is referred to as type II if the manic symptoms are less obvious and less severe (referred to as hypomanic). In type II the episode is not severe enough to cause marked impairment in social or occupational functioning, or to necessitate hospitalization, and there are no psychotic features.

It has been customary to think that bipolar type I disorder is more severe than bipolar type II. Certainly the manic symptoms are more severe by definition in type I versus type II. However, this study suggests that this view may not be correct. When you look beyond the manic episodes themselves, bipolar type II disorder appears to be more severe.

A history of hallucinations or delusions was present in one third of subjects, history of alcoholism in one third of subjects and suicidal behavior in one fifth of subjects.

Episode frequency was significantly associated with alcoholism and with a history of suicidal behavior. One of the most important things to accomplish in a bipolar patient who is drinking is to get the drinking stopped. Alcohol is a disinhibitor and makes mania worse. Alcohol also vastly increases the risk of suicide in otherwise depressed patients. In general, alcohol is a destabilizing influence in patients with bipolar disorder.

Somewhat surprisingly, thyroid disorders were not associated with increased frequency of episodes.

This is the first study which has demonstrated that episode frequency, defined as the number of depressive, hypomanic or manic episodes per year, is a familial trait in bipolar disorder. More frequent episodes is an indicator of greater severity and tends to be associated with other indicators of greater severity such as early age of onset, hallucinations and delusions, alcoholism, and suicidal behavior.

Episode frequency may turn out to be a useful way to sub-classify patients with bipolar disorder for genetic research. Studies examining twins with the disorder might be a logical next step to further demonstrate the heritability of this characteristic.

Okanagan Clinical Trials currently has two studies underway that are examining treatments for bipolar disorder. One is focusing on manic episodes and the other on bipolar depression. If you are an adult who experiences bipolar disorder, you may be interested in learning whether or not you are eligible for participation in one of these studies. Contact us at 862-8141 for more information.


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