The role of psychomotor activation in discriminating unipolar from bipolar disorders: a classification-tree analysis.
OBJECTIVE
Multiple studies indicate that bipolar disorders are often underrecognized, misdiagnosed, and incorrectly treated. The aim of the present report is to determine which combination of clinical, demographic, and psychopathological factors and corresponding cutoff scores best discriminate patients with unipolar disorder from those with bipolar disorders.


METHODS
The study sample includes outpatients and inpatients (N = 1,158) participating in 5 studies carried out in the United States and Italy between October 2001 and March 2008, one of which was a randomized clinical trial. Diagnostic assessment was carried out with the SCID, which allows diagnoses to be made according to DSM-IV-TR criteria. Using an exploratory statistical approach based on a classification tree, we employed 5 mania spectrum factors and 6 depression spectrum factors derived from the Mood Spectrum Self-Report Instrument (MOODS-SR) in combination with demographic and clinical characteristics to discriminate participants with unipolar versus bipolar disorders.


RESULTS
The psychomotor activation factor, assessing the presence of thought acceleration, distractibility, hyperactivity, and restlessness for 1 or more periods of at least 3 to 5 days in the lifetime, identified subgroups with an increasing likelihood of bipolar disorder diagnosis. Mixed instability and suicidality contributed to further subtyping the sample into mutually exclusive groups, characterized by a different likelihood of receiving a diagnosis of bipolar disorder. Of the demographic and clinical characteristics included in the analysis, only sex proved to be useful to improve the discrimination.


CONCLUSIONS
The psychomotor activation factor proved to be the most potent discriminator of those with unipolar versus bipolar diagnoses. The items that constitute this factor, together with those that constitute the mixed instability, suicidality, and euphoria factors, might be useful in making the differential diagnosis.
Department of Psychiatry, Neurobiology, Pharmacology, and Biotechnology, School of Medicine, University of Pisa, Pisa, Italy.
Giovanni B
GB
Cassano
Paola
P
Rucci
Antonella
A
Benvenuti
Mario
M
Miniati
Simona
S
Calugi
Luca
L
Maggi
Stefano
S
Pini
David J
DJ
Kupfer
Mario
M
Maj
Andrea
A
Fagiolini
Ellen
E
Frank
D000293:Adolescent; D000328:Adult; D000368:Aged; D001714:Bipolar Disorder / Q000175:diagnosis*; D003866:Depressive Disorder / Q000175:diagnosis*; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011595:Psychomotor Agitation / Q000175:diagnosis*