Dr. Suzanne King
Prenatal Maternal Stress From a Natural Disaster Predicts Thought Disorder in Adolescent Boys and in Those Exposed Later In Gestation: Project Ice Storm.
Background: Epidemiological studies find that maternal exposure to a major stressor in pregnancy increases the unborn child’s risk for schizophrenia in later in life, especially in males with mid-pregnancy exposure. But the mechanism is unknown: is it due to the objective degree of maternal hardship, or to the mother’s degree of distress? One symptom of schizophrenia is thought disorder which may be present in the general adolescent population along a continuum of severity. Would prenatal stress also explain variance in thought disorder in adolescence? We address this question using a prospective study of children exposed in utero to the January 1998 Quebec ice storm. The advantage of using a natural disaster as stressor in a prospective study is that disasters are “independent” stressors, that is, independent of the pregnant woman’s potential influence. Disasters also allow the researcher to distinguish between effects of the woman’s objective exposure, her cognitive appraisal of the event as negative or positive, and her degree of subjective distress. Aims: To determine the extent to which different components of prenatal maternal stress (objective, cognitive, subjective) explain variance in thought disorder at age 15, and the extent to which the association is moderated by child sex and timing of the storm in gestation. Method: In June 1998 women who were pregnant during the January 1998 ice storm answered questionnaires about their objective exposure to the disaster, their cognitive appraisal of it, and their subjective distress. At age 15, their children were interviewed about life stressors and recordings transcribed. We rated the verbalizations for thought disorder (TD) using the Communicative Disturbances Index (Docherty, 1996). Results: We regressed Thought Disorder on Objective hardship, subjective distress, sex, timing in utero, and interactions. Our models explained up to 23% of variance in TD. More severe objective exposure predicted more TD in boys (n = 31, r = 0.53*) but not in girls (n = 22) (Objective-by-Sex interaction, p = .01). Also, the effect of objective stress on TD increased in magnitude the later in pregnancy the teens were exposed, with significant effects after month 2 of pregnancy (Objective-by-Timing interaction, p = .02). Subjective-by-Timing interaction was also significant (p = .03), with subjective distress effects being significant with ice storm exposure from month 5 onwards. Discussion and conclusions: This is the first prospective study of prenatal maternal stress to demonstrate effects on subtle signs of thought disorder in adolescence. By using a natural disaster as stressor we were able to disentangle the effects of objective, cognitive and subjective maternal experience. The sudden-onset disaster also allowed precise timing of the onset of the storm in utero. Results highlight the importance of sex and timing in moderating the effects of both the objective and subjective aspects of prenatal maternal stress.