The psychological well-being of Norwegian adolescents exposed in utero to radiation from the Chernobyl accident

The accident at the nuclear power plant in Chernobyl on 26 April 1986 released large amounts of radioactive materials. Several areas of central Norway were heavily affected by far field radioactive fallout. The present study focuses on the individuals who were exposed to the radiation in these areas as fetuses. It is well documented that in utero exposure to a range of environmental toxins may have long-term consequences for neurodevelopment. Most studies have looked into the neurodevelopment effects of exposure to drugs, alcohol and cigarettes. In utero ionizing radiation exposure has received much less attention [1]. The effect of low-dose radiation on the fetus is unclear, and previous research on the neurological and psychological effects of in utero exposure to Chernobyl radiation has been inconsistent.

While the focus has been on the possible cognitive outcomes of in utero exposure to ionizing radiation, there has also been concern about psychological effects. Previous research on children exposed in utero to Chernobyl radiation found a higher incidence of both cognitive and psychiatric problems [2–4]. Other studies of children exposed as infants or in utero did not document any differences between those exposed and controls. However, mothers of in utero exposed children rated their children significantly higher on scales of memory problems, hyperactivity and somatic complaints [5–7]. In Kiev, the overall problem scores on the Child Behavior Checklist were generally high both for children evacuated to Kiev shortly after the accident and for controls who had resided in Kiev before the accident [5, 7].

Studies from Hiroshima and Nagasaki indicate that generalized and health-focused anxiety, somatization and depressive symptoms remained elevated for 10 to 20 years after the bombings [5]. Children studied after other disasters, particularly unexpected, severe, traumatic events, have demonstrated increased risk for internalizing and externalizing symptoms [5].

There is evidence for a significant effect of clinical morbidity in certain risk groups after toxicological accidents, especially anxiety disorders in mothers with young children and in evacuees [8]. Women, especially those who have young children to care for, appear to be more at risk for psychological health effects [8]. This heightened vulnerability also affects pregnant women. After the nuclear accident at Three Mile Island, women who lived near the facility and who were pregnant or had young children at the time were among those who experienced the greatest psychological distress [9].

Research of the developmental impact of disasters that involve in utero radiation exposure focus on two main routes of effect--in utero radiological exposures, and the effects of maternal stress on the developing fetus, or a combination of the two [10]. Being exposed to radiation as a result of a power plant accident is a stressful experience for pregnant women. The fact that radiation exposure events usually involve both elevated radiation exposure and higher levels of maternal stress makes it difficult to separate these two routes of effect.

A previous study examining neurocognitive functioning in Norwegian adolescents who were exposed in utero suggested lower IQ [11] and deficits in neuropsychological function compared with nonexposed adolescents [12]. The aim of the current study is to examine the emotional and behavioral functioning of these in utero exposed adolescents, as perceived by the adolescents themselves and their mothers. Will these adolescents and their mothers report elevated levels of problems? Are there significant differences between self-reports and maternal reports?

The current study, with a CBCL mean Total Problems score of 11.8, is in accordance with previous Nordic studies, which also reported low CBCL mean Total Problems scores in comparison with studies in other countries [18]. A Swedish study that examined 1308 school children aged 6-16 years old with the CBCL found a mean Total Problems score of 14.2 [19]. A Norwegian study of 1170 children aged 4-16 [17] found a CBCL mean Total Problems score of 15.4. For the subgroup aged 12-16, the mean Total Problems score was 13.6 [17]. In the current study rates of self-reported behavior problems (YSR) were generally higher for the adolescents, with a mean Total Problems score of 31.1, but within the normal range and lower than those reported in another Norwegian study [20].

The mothers' ratings reported low levels of problems and better psychological functioning than the adolescents reported themselves. Many researchers have reported significant discrepancies between youth-reported and parent-reported psychopathology in adolescents [21]. In studies of nonclinical samples, youths report higher severity ratings than their parents [21]. Our findings are consistent with previous studies comparing parent reports and youth self reports of adolescents' emotional and behavioral problems.

Investigations have documented Chernobyl-related psychological problems in prenatally exposed children in the former Soviet Union [2–4, 22]. The causes of these observed psychological problems are uncertain. The radiation release may have a direct, physiological impact on the developing fetal brain, and/or it may affect the fetus in terms of stress on the mother caused by the perceived danger of exposure to Chernobyl radiation. Other stressful consequences of the accident may also continue to affect the child later on. It is difficult to separate the potential impact of these variables.

In the former Soviet Union, the accident had a tremendous impact on the areas surrounding Chernobyl, both in terms of radiation exposure and psychosocial consequences interfering with people's lives. However, some investigations did not document a rise in psychological and behavioral problems in children exposed in utero or as infants in these areas [5, 6]. In one study [5], evacuees and non-evacuees obtained high scores on the CBCL problem scale but there were few significant differences between groups. Among the significant differences were maternal ratings of somatic complaints. Evacuee mothers rated their children's well-being as significantly worse, especially on somatic symptoms on CBCL [5]. The most important risk factors for these ratings were somatization and Chernobyl-related stress experienced by the mother. Another study revealed no significant differences between groups related to level of radiation exposure, but mothers who were pregnant at the time of the accident rated their children as significantly more hyperactive [6]. Interestingly, in the Taormina study [7], evacuee mothers were almost three times more likely to report their children as having memory problems.

In the current data mothers rated their children as having fewer problems than the adolescents themselves reported. This pattern is typical in nonclinical groups. This could indicate that the mothers included in the current study were less worried than the mothers in previous investigations of radiation exposed individuals.

People have a strong tendency to worry about their future health once they know they have been exposed to radiation, even when the dose they have received is negligible [23]. The amount of radiation discharged from the accident at Three Mile Island in the United States was less than one-millionth of the release from the Chernobyl accident, but the Three Mile Island accident seriously affected the mental health of the general population [24]. Why does this not seem to apply to prenatally exposed Norwegians and their mothers?

The passage of time may affect the psychological reactions. Five years after the nuclear accident at Three Mile Island, the mental health of women who were living close to the site and were pregnant at the time of the accident was similar to that of women from the same area who became pregnant after the accident. Maternal ratings of the two groups of children when they were five years old were also similar [9]. In a study of in utero exposed children from the former Soviet Union, Korol and Shibata [22] found the prevalence of neurotic disorders to be significantly higher in the in utero exposed group from 1989-1997, but the difference diminished in effect from 1999-2003. These findings suggest that the psychological effects change over time. Differences in the timing of investigations may be one explanation of inconsistent findings across studies. The low levels of problems reported in the current study may be explained by the two decades that separated the accident and the investigation.

In a survey study [25] estimating Chernobyl-related anxiety among Norwegians in the first two months following the accident, the anxiety and stress produced by the accident only reached clinical levels for about 1% of the respondents. Studies that have investigated the effects of toxicological disasters provide evidence of a significant increase in the number of legal abortions [8], but there was no rise in legal abortions in Norway in the year following the Chernobyl accident [26]. These findings suggest that even though the accident and its consequences in Norway were well known, Norwegians were less worried about the potential impact of exposure to Chernobyl fallout.

Johnson and Galea [10] have described risk factors associated with mental health problems after disasters. Among these are: direct exposure to the disaster; the degree of exposure to and direct threat from the disaster; participation in rescue and cleanup; media exposure; indirect consequences of the disaster (such as relocation or residential problems and community destruction); proximity to the disaster; being in the disaster-affected area at the time of the disaster; alcohol-related problems since the disaster; events since the disaster; negative life events; demographics; low-medium socioeconomic status or education level; social factors; limited post-disaster help; perceived similarity to victims; and perceived risk.

The risk factors mentioned above were higher for the exposed population from the former Soviet Union than for the Norwegian population living in exposed areas, with the most obvious difference being proximity to the disaster. The exposed population in the former Soviet Union experienced a lack of information, disorderly evacuation, conflicts over housing and benefits, and inadequate medical care [5]. Because of the collapse of the former Soviet Union, there were dramatic changes in the socioeconomic environment as well [23]. This can explain the fact that even though researchers did not document differences between evacuees and controls in Kiev, CBCL problem scores were generally high for both groups [5, 7].

The Norwegian authorities provided systematic measures of ionizing radiation, adequate information about the potential dangers, restrictions on certain kinds of polluted foods, readily available health care and economic compensation for farmers in affected areas. There was no evacuation as a result of the accident. As in the rest of Norway, the participants in this study came from families that enjoyed a high living standard and social security. Higher social class, usually measured by education and income, is associated with better mental health outcomes after accidents [8]. It is likely that these factors have served as a protective buffer against the potentially harmful psychological effects of the accident on Norwegians. The perception of physical and psychological distance from the accident has probably had a protective effect as well.

The results presented here demonstrate a contrast to previous studies of children exposed prenatally to Chernobyl radiation. In spite of previous reports of subtle cognitive deficits in prenatally exposed Norwegians, self-reported problems were few, and problems reported by the mothers even fewer. This is an unusual pattern, compared with other studies of prenatally exposed children from the former Soviet Union. Most studies have reported some kind of problems as measured by self report, and from the mothers of in utero exposed children. A possible explanation for this discrepancy between investigations is that the mothers of the Norwegian participants experienced less Chernobyl-related anxiety, due to fortunate circumstances in Norway and perceived physical and psychological distance from the disaster. This may have served as a buffer against a negative impact on the psychological health of both mother and child. Other explanations of the few problems reported may be the passage of time since the disaster, cultural differences between participants in the different investigations and/or lack of data in the current study. This study confirms previous findings of low levels of child behavior problems in Norway. The data do not suggest negative long-term effects on emotional and behavioral functioning as reported by these adolescents and their mothers in relation to in utero exposure to Chernobyl fallout.