Clinical features that can appear many years ahead of a psychiatric diagnosis may help doctors to predict whether patients will develop bipolar disorder or unipolar depression, say researchers.
“The need for such differential prognosis is commonly encountered clinically, particularly in young patients”, observe Ross Baldessarini (McLean Hospital, Belmont, Massachusetts, USA) and study co-authors.
Many of the antecedents appeared during childhood. For example, in semi-structured clinical interviews, 6.51% of 215 patients with bipolar disorder recalled having phobia between the ages of 1 and 12 years, whereas none of the 119 patients with unipolar depression did so.
Hyperactivity/restlessness and mood swings during childhood were also more common in patients with bipolar disorder than unipolar depression. But generalised anxiety was more frequent among the depressive patients, at 15.10% versus 6.98% of those with bipolar disorder, and this was also true during adolescence.
A “striking finding” was that depressive symptoms were more common among patients with bipolar disorder than those with unipolar depression, at 11.6% versus 4.2% during both childhood and adolescence.
“This association may be less surprising if the critical aspect is timing in early life rather than the depressive nature of the symptoms”, the researchers write in the Journal of Affective Disorders.
Substance abuse during adolescence was an antecedent of bipolar disorder (12.1%) but not of unipolar depression.
“[I]t is important to note that many of the identified antecedents, individually, occurred at quite low frequency with variable overlap between [bipolar disorder] and [unipolar depression] subjects”, say Baldessarini and team.
“Moreover, many identified features occur in the general population and may be associated with a variety of morbid outcomes or with absence of diagnosable adult psychiatric illness.”
Indeed, the predictive power of individual antecedents was low. For example, depressive symptoms during childhood or adolescence was 95.8% specific for bipolar disorder versus unipolar depression, but only 11.6% sensitive.
However, combining antecedents improved predictive power. The presence of at least three or four antecedents was between 63.6% and 83.3% sensitive and was 58.8% to 84.9% specific for bipolar disorder, correctly classifying between 71.0% and 74.6% of patients.
“Having greater confidence in predicting later [bipolar disorder] should prove valuable in formulating prognosis and in organizing supportive and psychoeducational interventions aimed at limiting risk of future morbidity, disability, and self-injury or suicide as clinical circumstances may require”, say the researchers.
They add that it may also help guide appropriate use of antidepressants, limiting their use as a monotherapy in patients likely to have bipolar disorder.
This article first appeared on ‘MedWire News’ on 20 November 2014.