The methods for COBY have been described in detail elsewhere.4 (link), 7 (link) Briefly, youth ages 7 to 17 years 11 months with Diagnostic and Statistical Manual-IV (DSM-IV) bipolar-I, II, and operationally 4 (link), 7 (link) defined bipolar-NOS were included. Youth with COBY-defined bipolar-NOS were previously shown to convert to bipolar-I/II and have a comparable, but less severe clinical picture, and similar family history, rates of comorbid disorders, and longitudinal outcome as compared to bipolar-I subjects.4 (link), 7 (link)
Youth with schizophrenia, mental retardation, autism, and mood disorders secondary to substances, medications or medical conditions were excluded.
Subjects were recruited from outpatient clinics (67.6%), inpatient units (14.3%), advertisement (13.3%), and referrals from other physicians (4.8%), and were enrolled independent of current mood state or treatment status.
The analyses presented in this report are based on the prospective evaluation of 413 subjects, including 244 (59.1%) with bipolar-I, 28 (6.8%) with bipolar-II and 141 (34.1%) with bipolar-NOS who had at least one follow-up assessment. At the time this article was written, subjects had been prospectively interviewed every 37.5±20.8 weeks for an average of 191.5 ± 75.7 weeks. Subjects with bipolar-II were followed significantly longer (227.4±76.6 weeks) than the other two bipolar subtypes (bipolar-I: 183.2±71.8 weeks, bipolar-NOS: 198.7±79.8 weeks) (F=5.4, p=.005).
As described in more detail in a prior publication, 7 (link) at intake subjects with bipolar-NOS were the youngest, followed by subjects with bipolar-I and then those with bipolar-II (Table 1). More youth with bipolar-NOS were in Tanner stage-I of sexual development than those with bipolar-II and more subjects with bipolar-II were Tanner IV/V than those with bipolar-I and -II. The mean age-of-onset for mood symptoms and DSM-IV mood episodes was 8.4 and 9.3 years, respectively (for definition of age-of-onset see below). Subjects with bipolar-II had the onset of their mood symptoms and episodes significantly later than the other two bipolar subtypes. As expected, by definition, the polarity of the index episode reflected the bipolar subtype with mania or hypomania being more common in youth with bipolar-I than those with bipolar-II or NOS. However, youth with bipolar-II had significantly more depressive index episodes that the other two bipolar subtypes. Subjects with bipolar-I had more lifetime psychosis than those with bipolar-NOS (for all above comparisons p-values <.05, Cohen’s d: 0.3–0.9). There were no other significant between group differences.
The subject retention rate at the time this manuscript was written was 86%, with 93% of subjects completing at least one follow-up interview. Except for lower rates of anxiety disorders in subjects who dropped from the study (54.5%, vs. 38.7%, p=0.02) there were no other demographic or clinical differences between the subjects who continued or withdrew from COBY.