Baseline demographic and clinical characteristics of the sample are shown in . Only 12.8% and 11.7% of patients reported high or moderately high baseline occupational functioning, respectively. The majority of participants reported average (25.5%) or below average (27.7%) functioning, and 22.3% reported poor occupational functioning at study entry. No significant differences in baseline vocational functioning were observed between participants initially assigned to interpersonal and social rhythm therapy and those assigned to intensive clinical management (3.35 [SD=1.30] versus 3.38 [SD=1.37], respectively), nor between male and female participants (3.47 [SD=1.25] versus 3.28 [SD=1.33], respectively). Mean time spent in the acute phase was 35.9 weeks (SD=21.7) for interpersonal and social rhythm therapy and 34.9 weeks (SD=20.9; p=0.79) for intensive clinical management.
Baseline Demographic and Clinical Characteristics of Patients Assigned to Acute Phase Interpersonal and Social Rhythm Therapy Versus Intensive Clinical Management
The main effect of initial treatment assignment did not reach conventional levels of statistical significance; however, we did observe a significant initial treatment by time interaction such that participants assigned to acute phase interpersonal and social rhythm therapy showed significantly more rapid initial improvement in occupational functioning than those initially assigned to intensive clinical management (F=4.08, df=1, 111, p=0.046). The improvement tended to be sustained during the maintenance phase, irrespective of the type of psychosocial treatment to which the participant was assigned during that phase. We observed no effect of maintenance treatment assignment. Although participants assigned to intensive clinical management in the acute phase showed much slower improvement in occupational functioning, by the end of 2 years of maintenance treatment their occupational functioning was virtually identical to that of participants assigned to acute phase interpersonal and social rhythm therapy ().
Change in Occupational Functioning Over Course of Acute and Maintenance Treatment in Patients Assigned to Acute Phase Interpersonal and Social Rhythm Therapy Versus Intensive Clinical Managementa
The repeated measures mixed-effects model showed a significant three-way interaction over the four time points among acute treatment assignment, gender, and time (F= 3.06, df=3, 104, p=0.032). The analysis was repeated, stratified by gender, and showed a significant treatment by time interaction in female participants (F=4.66, df=3, 64.2, p= 0.005) but not in men (F=1.42, df=3, 40.7, p=0.25). illustrates the observed scores across time by acute phase treatment assignment and gender. The significant interaction among women is accounted for by the difference at the end of the acute treatment phase, with participants initially assigned to interpersonal and social rhythm therapy performing significantly better occupationally than those initially assigned to intensive clinical management.
Change in Occupational Functioning By Gender Over Course of Acute and Maintenance Treatment in Patients Assigned to Acute Phase Interpersonal and Social Rhythm Therapy Versus Intensive Clinical Managementa
No significant differences in educational attainment, age, or number of prior depressive or manic episodes were found between male and female participants. Differences were observed, however, in the occupations of men and women. Not surprisingly, all of those categorized as homemakers were women, while men accounted for almost three-fourths of those reporting sales as their occupation. Women who were homemakers showed significantly worse occupational functioning at baseline (t= –3.15, p=0.002) than other occupational groups, but no differences in occupational functioning were observed among the various occupational categories at the subsequent time points.
In order to explore possible explanations for the observed gender difference, we conducted additional analyses to examine whether this difference could be accounted for by improvement among women who were homemakers only (who are, in essence, accountable only to themselves and their families and are not dependent on the evaluation of external employers). We found no evidence that improvement among homemakers only accounted for the gender difference in outcomes (t=1.23, df=45, p= 0.23); however, homemakers did improve more on average (0.9 [SD=1.0] versus 0.3 [SD=1.4]).
We also questioned whether this effect could be explained by a history of more antisocial behavior among the male participants (which might have made them less employable, even after symptomatic recovery). Using data from the antisocial personality probes of the SCID, we found no differences between men and women in this study in terms of the number of positive probes for antisocial personality criteria, nor did men and women in this sample differ in terms of the probability of having a lifetime diagnosis of drug abuse or dependence disorder (14% for men versus 18% for women). However, male participants were significantly more likely to have a lifetime diagnosis of alcohol abuse or dependence disorder (36% for men versus 17% for women; χ2=7.70, p=0.006).
Finally, we were interested in whether occupational functioning is simply a surrogate measure of clinical outcome, which would mean that our findings were simply a reflection of the better clinical outcomes resulting from initial assignment to interpersonal and social rhythm therapy, as documented in our original report on this trial (13
). To test whether improvement in occupational functioning was the actual mediator of the longer time to recurrence observed in those initially assigned to interpersonal and social rhythm therapy, we conducted a Cox proportional hazards model, using time to recurrence as outcome and occupational functioning at 1 year as predictor (data not shown). Worse occupational functioning predicted shorter time to recurrence but only explained a small percent of the variation (R2
=0.056). Thus, the benefits of initial assignment to interpersonal and social rhythm therapy for time to recurrence and for occupational functioning appear to be largely independent effects.