A family history of bipolar, psychotic, or substance use disorders best differentiates adolescents and young adults with emerging bipolar disorder from those with unipolar depression, say Australian researchers.
Furthermore, increased social anxiety levels differentiate adolescents and young adults with unipolar depression from those with emerging bipolar disorder.
"Early in the course of illness, clinical features of depression, or neuropsychological function, do not readily differentiate the two illness trajectories," comment Ian Hickie and colleagues from the University of Sydney.
The findings come from a study of 308 patients, aged between 12 and 30 years, with affective disorders.
All of the patients were assessed for mania/hypomania or illness course consistent with a bipolar spectrum disorder in interviews with psychiatrists or clinical psychologists. They also underwent comprehensive clinical and neuropsychologic assessments.
Overall, 30% (n=90) of the participants met criteria for a bipolar-type syndrome, the researchers report in the Journal of Affective Disorders.
Bipolar and unipolar groups were similar in terms of current mean age (19.8 vs 19.2 years) and age at onset (14.5 vs 14.3 years). Both groups also had similar levels of psychologic distress, depressive symptoms, current role impairment, neuropsychologic dysfunction, and alcohol or other substance misuse.
However, patients with a bipolar-type syndrome were significantly more likely than unipolar patients to have a family history of bipolar disorder (21 vs 11%), psychosis (19 vs 9%), or substance misuse (35 vs 23%).
Conversely, patients with unipolar disorders had higher levels of social anxiety than those with bipolar-type syndromes, with scores on the Social Interaction Anxiety Scale of 38.2 versus 33.4.
There was no significant difference between the groups regarding patterns of psychiatric comorbidity, although there was a trend toward more concurrent 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," conclude Hickie et al.
They add: "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."
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