Bipolar disorder is common among Japanese patients with panic disorder, research shows.
Tsukasa Sasaki (University of Tokyo, Japan) and colleagues found that 22.3% of 649 patients (434 women) with panic disorder met criteria for, or had a previous diagnosis of, bipolar I (BD I) or II (BD II) disorder.
This is much higher than the lifetime prevalence of BD in the general population of Japan, estimated at 0.2%, they say. The researchers warn that "the actual figure could be higher when a broader range of bipolar spectrum disorders is included."
The findings are important, "especially considering that antidepressants are the first line of treatment for panic disorder," they add.
All of the patients, who had a mean age of 38 years, were attending anxiety disorder clinics in Tokyo or Nagoya.
The Mini-International Neuropsychiatric Interview (MINI) and clinical records were used to assess the participants for panic disorder, BD, and presence of suicidality.
The patients were also assessed using the State Trait Anxiety Inventory-Trait scale (STAI-T) and the Anxiety Sensitivity Index (ASI), and completed the self-report Revised Neuroticism-Extraversion-Openness Personality Inventory (NEO-PI-R).
Overall, 17.1% of patients had BD II and 5.2% had BD I, the researchers report in the Journal of Affective Disorders.
Patients with BD I had a higher prevalence of suicidality than patients with BD II and those without BD, at 44.1% versus 27.0% and 21.4%, respectively.
Patients with BD I also had higher STAI-T scores than patients with BD II and those without BD (59.8 vs 51.8 and 47.9, respectively) and higher ASI scores (53.4 vs 45.3 and 41.3, respectively).
In addition, patients with BD I had higher NEO-PI-R scores for neuroticism and lower NEO-PI-R scores for agreeableness than patients with BD II and those without BD, at 135.7 versus 119.1 and 108.4, and 98.3 versus 108.0 and 112.2, respectively.
"The present study suggested a significantly elevated prevalence of bipolar disorders in panic disorder," comment Sasaki and team.
They conclude that clinicians should consider the possible presence of BD in the treatment of patients with panic disorder.
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