A family history that includes bipolar, psychotic, or substance use disorders points more toward the possibility of bipolar disorder, while increased social anxiety levels point toward unipolar depression.
“Early in the course of illness, clinical features of depression, or neuropsychological function, do not readily differentiate the two illness trajectories,” said researchers.
For the study, researchers evaluated 308 patients, ages 12 to 30 years, with affective disorders. All of the participants were assessed for mania and hypomania, or an illness consistent with a bipolar spectrum disorder during interviews with psychiatrists or clinical psychologists. They also received comprehensive clinical and neuropsychologic assessments.
Overall, 30 percent of the patients met criteria for a bipolar-type syndrome, the researchers reported in the Journal of Affective Disorders.
Bipolar and unipolar patients were similar in terms of current mean age (19.8 vs 19.2 years) and age at onset (14.5 versus 14.3 years). Both groups also had similar levels of psychological distress, depressive symptoms, current role impairment, neuropsychological dysfunction, and alcohol or other substance misuse.
However, participants with a bipolar-type syndrome were significantly more likely than unipolar patients to have a family history of bipolar disorder (21 vs. 11 percent), psychosis (19 vs. 9 percent), or substance misuse (35 vs. 23 percent).
Furthermore, individuals with unipolar disorders had higher levels of social anxiety than those with bipolar-type syndromes.
There was no significant difference between the groups in patterns of having co-existing psychiatric conditions (comorbidity), although there was a trend toward more co-existing anxiety disorders in those with unipolar disorders.
“While a range of clinical features are often reported to be characteristic of patients with bipolar disorders… in this study only family history of non-depressive disorders (bipolar, psychotic, substance misuse) in the bipolar group, and higher current social anxiety in the unipolar group, discriminated the two illness types,” said researcher Ian Hickie.
The researchers added, “This study highlights the challenges faced by those who wish to recruit subjects to early intervention studies designed to reduce the risk of progression to bipolar disorders.”
Source: Journal of Affective Disorders