There were no statistically significant group differences between OBP (n = 31) and OHC (n = 21) participants in age (mean years = 9.9 ± 2.4 vs. 10.1 ± 1.5, p =0.50) or sex (female, 48% vs. 38%, Fisher's exact test, p = 0.57). There were more White subjects in the OBP group than in the OHC group (94% vs. 71%, Fisher exact test, p = 0.05), but our results were unchanged after analyses were adjusted for ethnicity (unadjusted results are reported). Twenty six (84%) of the OBP had at least one DSM-IV Axis I disorder; 19 (61%) OBP had at least one mood disorder, including dysthymia (n = 5), major depressive disorder (n = 4), bipolar I disorder (n = 5), bipolar II disorder (n = 4), cyclothymia (n = 2), and bipolar disorder not otherwise specified (n = 1); 12 (39%) OBP had a diagnosis of ADHD; and 7 (23%) OBP had co-occurring bipolar disorder and ADHD.
Compared with OHC, OBP had a significantly increased mean Activity Level–General score (t = 2.97, df = 50, p = 0.005, d = −0.78), and a trend for a decreased mean Task Orientation score (t = −2.68, df = 50, p = 0.01, d = −0.78) (). There is significantly greater variability in the OBP group on the Activity–General (Levene test of homogeneity of variances, F(1,50) = 7.97, p = 0.0068) and Mood subscales (Levene test of homogeneity of variances, F(1,50) = 8.05, p = 0.0066) than the OHC group. In addition, OBP without a mood disorder showed trends for significantly higher subscale scores in Approach (t = 2.44, df = 29, p = 0.02, d = 0.89), Flexibility–Rigidity (t = 2.73, df = 29, p = 0.01, d = 1.01), Rhythmicity–Sleep (t = 2.15, df = 29, p = 0.04, d = 0.79), and Task Orientation (t = 2.31, df = 29, p = 0.03, d = 0.89) as compared to OBP with a mood disorder. Trends for increased mean Task Orientation scores were also found in OBP without ADHD versus with ADHD (t = 2.25, df = 29, p = 0.03, d = 0.82).
Mean Comparisons of DOTS-R Scores: Offspring of Parents with Bipolar Disorder, Healthy Offspring of Healthy Parents, and Offspring of General Population
YMRS and IDS scores were significantly higher in the OBP versus OHC group [OBP, mean (SD) = 4.1(5.5) versus OHC = 0.57(1.1), t = 3.48, df = 49, p < 0.002 and OBP, mean (SD) =5.9(7) versus OHC = 2.1(5), t = 2.21, df = 49, p = 0.03, respectively]. Within OBP, more severe mania symptoms were significantly correlated with Flexibility–Rigidity (r = −0.46, p = 0.01, d = 0.52), Activity Level–General (r = 0.64, p = 0.0001, d = 0.83), Activity–Sleep (r = 0.56, p = 0.001, d = 0.68), Rhythmicity–Sleep (r = −0.45, p = 0.01, d = 0.50), and Task Orientation (r = −0.54, p < 0.002, d = 0.64) subscale scores. There were 4 subjects among the OBP with a YMRS score of 10 or greater. IDS scores were significantly correlated with Mood (r = −0.66, p < 0.0001, d = 0.88) within the OBP group. There were no significant correlations within the OHC group between DOTS-R subscale scores and YMRS (highest r = 0.40, p = 0.07, d = 0.44 for Rhythmicity–Eating) or IDS (highest r = 0.34, p = 0.13, d = 0.36) scores.
DOTS-R normative data (Windle 1992
) are sampled from 972 families across the United States and did not exclude families by the presence of parental or child psychiatric illness. We compared these normative data with our OBP sample (). Our OBP group reported lower Activity Level–General (Z
= −2.63, p
= 0.009) and Rhythmicity–Daily Habits (Z = −5.61, p
< 0.0001) scores, and higher Rhythmicity–Sleep (Z = 3.85, p
= 0.0001) scores than the US normative control group. We also compared the DOTS-R normative data with our OHC group. Our sample of OHC reported lower Activity Level–General (Z = −5.85, p
< 0.0001) and Activity Level–Sleep (Z = −3.64, p
< 0.0003) scores, and higher Task Orientation (Z
= 2.93, p
< 0.003), Rhythmicity–Sleep (Z = 4.13, p
< 0.0001), and Rhythmicity–Eating (Z = 3.13, p
< 0.002) subscale scores than the U.S. normative control group.