The demographic characteristics of the cohort are given in . The majority of women were between 20 and 34 years old (69%), completed college (57%), were non-Hispanic white (80%), married (74%), and had planned their pregnancy (64%). However, a substantial minority did not fit these characteristics. Of the 838 women, 349 (42%) had no prior live births.
Population Characteristics (n=838)
The rates of affirmative endorsement for at least one stem question, by trimester were 9% (n=72), 5% (n=41) and 3% (n=27). Rates of medication use were 12% (n=98), 9% (n=71) and 8% (n=62),. Both probable rates of depression (p<.0001) and rates of medication use (p=.02) differed significantly across trimesters. After application of standard CIDI diagnostic algorithms, only 2 women had MDD in every trimester, and 5 women had either MDD or minor depressive disorder (MinD) in every trimester. Comparatively, 779 (93%) women had no reported MDD and 733 (87%) women had no MDD or MinD.
Positive responses to the stem questions tended to cluster together. The number of positive responses to the stem questions decreased over time but this pattern of clustering held during subsequent trimesters. The CIDI considers “sad” and “discouraged” as one item and thus we grouped these together. In the first trimester, 58 (7%) women responded affirmatively to the “sad/discouraged” stem questions as well as the “uninterested” stem question. These rates were 32 (4%) and 19 (2%) in the second and third trimesters, respectively. Only 14 (2%) endorsed either “sad/discouraged” or “uninterested” questions in the first trimester, 9 (1%) in the second trimester and 8 (1%) in the third trimester.
Crude symptom rates decreased after the first trimester () while endorsement of symptoms varied widely. For example, 73% of the population experienced “decrease in energy” in the first trimester compared to 3% who were “feeling jittery”. In the second and third trimesters these percentages dropped to 31% and 29% for “decrease in energy” and 1% and 2% for “feeling jittery” in the second and third trimesters, respectively. Most of the other symptoms showed similar decreases after the first trimester. On average, participants endorsed 3.29 symptoms (95% CI: 3.15—3.43) in the first trimester compared to 1.79 (95% CI: 1.66—1.93) in the second trimester and 1.41 (95% CI: 1.29—1.53) in the third.
Observed Symptom Frequencies by Trimester
Odds ratios for expression of symptoms during the first trimester compared to the second and third trimester are presented in . These results controlled for endorsement of stem questions (Y/N) and medication use in an attempt to understand the effects of pregnancy independent of stage of pregnancy or medication use. Eight of the thirteen symptoms, including “appetite decrease”, “appetite increase”, “oversleeping”, “decrease in energy”, “moving slowly”, “thinking slowly”, “racing thoughts”, and “trouble concentrating” were significantly higher in the first trimester than the second and third, respectively. Additionally, “trouble sleeping” was significantly higher in the first trimester compared to the third, and “feeling jittery”, “indecisive”, and “feeling guilty/worthless” were significantly higher in the first compared to the second trimester. The exception was that the symptom “increase in energy” was slightly lower in the first trimester compared to the second.
Odds Ratios of Trimester Differences for Behavioral and Cognitive Symptoms
Overall, women who responded affirmatively to a stem question for MDD had more symptoms than women who did not offer a positive response to these symptoms. Women who were treated with antidepressant medication had only slightly more symptoms than non-medicated women (see ). Ten of thirteen symptoms, including “appetite decrease”, “trouble sleeping”, “decrease in energy”, “moving slowly”, “feeling jittery”, “thinking slowly”, “racing thoughts”, “trouble concentrating”, “indecisive”, and “feeling guilty/worthless” had significantly higher occurrence in the stem question-positive group compared to the stem question negative group. Four of the thirteen symptoms, “oversleeping”, “decrease in energy”, “racing thoughts”, and “trouble concentrating” had significantly higher rates for women who took medication compared to the non-medicated group.
Odds Ratios of Depression and Medication Use for Behavioral and Cognitive Symptoms
The ROC analysis indicated that the optimal threshold of the EPDS for detection of an individual who has a probable CIDI diagnosis of MDD was 10 in all three trimesters. (see ). Sensitivity and specificity were slightly higher in the second trimester while positive predictive value dropped in the third trimester due to the small number of cases.
Summary Statistics for the EPDS ROC Analysis
Finally, there was generally good agreement between the standard DSM IV and the Zimmerman criteria for a diagnosis of MDD, although agreement varied across pregnancy (see ). The Zimmerman criteria identified 40 (5%), 20 (2%), and 11 (1%) subjects as in episode for MDD during the first, second and third trimesters, respectively. After application of the standard DSM IV criteria, 42 (5%), 25 (3%), and 10 (1%) were diagnosed with MDD, respectively during the first, second and third trimester. The corresponding Kappa statistics were 0.82 (95% CI: 0.72--0.91) in the first trimester, 0.79 (95% CI: 0.66--0.93) in the second trimester and 0.86 (95% CI: 0.69--1.00) in the third trimester.
Concordance between Zimmerman MDD and Full DSM-IV MDD