Illness Factors Inform Suicide Risk in Bipolar and Depressive Disorder Patients
Despite patients with bipolar disorder having a higher recorded prevalence of suicide attempts when compared to those with major depressive disorder (MDD), a new study suggests the different illnesses may not be the reason for the differential rates.
According to a new report published in Bipolar Disorders, the higher prevalence of suicide attempts in patients with bipolar disorder can be explained by a lower age at onset and longer duration of illness, rather than the illness itself.
Researchers, led by Erkki Isometsa and colleagues from the University of Helsinki in Finland, explained that the difference in onset and longer duration of illness caused a higher number of total illness episodes and a greater proportion of time spend in major depressive episodes (MDEs).
This implies that “diminishing the relative time spent in high-risk phases appears crucial for prevention of suicide acts,” as the researchers state in their report.
The researchers pooled data from 176 patients with bipolar disorder and 249 patients with MDD who were in the process of participating in the Jorvi Bipolar Study and the Vantaa Depression Study, respectively.
Prior to the study, 51 percent of patients with bipolar disorder reported attempting suicide, compared with 33 percent of those with MDD. During the first 18 months of follow-up, the researchers saw the respective suicide rates were 20 percent and 10 percent.
However, the researchers also found that the median length of preceding illness was over seven years longer for patients with bipolar disorder compared to those with MDD. Not only that, but the age of onset was 10 years younger. Lastly, the researchers noted that patients with bipolar disorder spend more time in MDEs than those with MDD, although they did spend less time with sub-threshold depression.
Most importantly, the team saw that suicide attempts did not differ significantly among patients with different forms of bipolar disorder or MDD overall, but instead the rates were highly dependent on mood phase.
The team used euthymia as a reference and noticed that the incidence of suicide attempts increased 5-fold during sub-threshold depression, 25-fold during MDEs and 65-fold during combined mixed episodes, regardless of illness type. However, the team did mention that the time spent in mixed phase was relatively short and therefore would have a smaller influence on the total risk of a suicide attempt.