MONTREAL – Cognitive, behavioral, and physical problems still persist today in a group of children exposed to prenatal stress during the Quebec ice storm of January 1998, according to research presented at the annual meeting of the International Society for Traumatic Stress Studies.
"The fetus is not immune to a certain amount of stress, which can be transmitted – probably biologically – from the mother, with resulting cognitive, emotional, physical, and motor development problems," reported Suzanne King, Ph.D., associate professor of psychiatry at McGill University and director of the psychosocial research division of the Douglas Hospital, both in Montreal.
The study measured subjective stress and objective hardship in 150 women during the ice storm, which was described as "the worst natural disaster in Canadian history" by the Insurance Bureau of Canada.
During the midwinter storm, 3 million people were left with no electricity, some for as long as 45 days, and 454 shelters were set up to house more than 17,000 people.
The study is the first prospective analysis of the effects of stress from a natural disaster on pregnant women and their children, said Dr. King. It used questionnaires to measure subjective and objective maternal stress during the storm, and then followed the offspring at 6 months, 2 years, 5.5 years, and 11.5 years.
From a sample of 1,440 women, only 224 responded (15%), and 150 completed the study. "Our resulting sample ended up being a highly educated group with a higher socioeconomic standard than average, which adds significance to the findings," she said.
On average, women in the study were without electricity for 15 days (range, 0-45) and without telephone contact for 4 days (range, 0-34). Two-thirds of them were forced to leave their homes during the storm, and possible posttraumatic stress disorder was present in 4%-17%, said Dr. King.
Although the rates of postpartum depression and premature birth (before 37 weeks) were within normal ranges at 17% and 8%, respectively, there was evidence of compromised cognitive development in the offspring at 2 years, with an odds ratio of 4.4 for delayed development in offspring exposed to high versus low levels of maternal objective stress. "This was controlling for subjective stress, which did not have a significant impact on this outcome. This was objective stress – just the facts – what happened to them," she said.
Additionally, at 2 years, there was a 10-point difference in IQ levels between these two sets of offspring, and these differences persisted at 8.5 years, the most recent data available.
In terms of subjective stress, high levels of maternal subjective stress were associated with increasing levels of offspring internalizing problems such as anxiety and depression, and externalizing problems such as aggression, she added.
"The kids are doing very well because they are from such highly resourced families – their IQs are still quite high, they’re above average – but even in these families we see this significant effect."
Additionally, an analysis of autisticlike symptoms at 6.5 years showed an interaction between both maternal stress and trimester of pregnancy. "For kids who were exposed to stress during the first trimester only, there were increasingly severe autisticlike symptoms with increasing objective stress. None of these kids are autistic, or even close, but in terms of these types of traits we are seeing an effect."
The researchers also examined dermatoglyphic asymmetry of fingertip ridges, a characteristic found more commonly in schizophrenia than in healthy individuals, which may reflect fetal disruptions in development between weeks 14 and 26. This finding was more common among offspring of mothers exposed during this period of their pregnancy, compared with children of mothers exposed during a different period (Dev. Psychopathol. 2009;21:343-53).
Dr. King and her group believe that much of the effect of maternal prenatal stress on an offspring’s cognition and emotional development is a result of direct effects on the fetal brain. In fact, when computational analysis of high-resolution structural magnetic resonance images was used to assess individual and group differences in brain structure, there was a decrease in hippocampal volume observed in boys, but not in girls. "The hippocampus is the part of the brain that is involved in stress reaction, memory, and emotions," she explained.
Similarly, an analysis of breastfed versus nonbreastfed infants during and after the ice storm showed a link between breastfeeding and decreased hippocampal volume, decreased salivary cortisol stress response, and increased internalizing problems in offspring aged 11.5 years, the group reported in a poster at the meeting.
Session chair Yael Danieli, Ph.D., said Dr. King’s study underscores the necessity of taking a full family history when assessing cognitive and psychological problems. "For a complete assessment of a human being’s state of health, one has to know a full history of trauma of prior generations," Dr. Danieli, a New York clinical psychologist, past president of the ISTSS, and editor of the International Handbook of Multigenerational Legacies of Trauma (1988), said in an interview.