Background
Somatic complaints are common among children and adolescents [
1,
2]. Danish as well as international studies have shown that up to 40% of adolescents have experienced pain related to the neck, back, or shoulder during the previous week [
2‐
4]. Between 20 and 30% of adolescent girls in the US experience symptoms such as headache, stomach ache, back pain and morning fatigue more than once a week [
5]. Somatic complaints seem to increase steadily both in total number and severity through childhood [
2,
6], and between one-third and half of children who report somatic symptoms continue to report symptoms as adults [
7].
Experiencing somatic symptoms in childhood and adolescence has several negative consequences for a person’s later health and social life [
8,
9]. A bidirectional association between somatic symptoms and depressive symptoms or anxiety has been documented as well as the possibility that these different symptoms are variants of the same primary disorder [
8,
10]
. Moreover, a previous Danish study found an association between somatic symptoms in adolescence and later reduced labour market participation [
11]. In order to prevent these negative consequences later in life, it is relevant to identify childhood conditions related to the development of somatic symptoms.
Previous studies have shown that low family socioeconomic position is associated with higher rates of somatic symptoms among their children [
5]. Furthermore, it seems that a negative parent-child relationship can affect the psychosomatic well-being of the child. A review by Eminson et al. documented that, in clinical samples, the outcome of treatment of somatic symptoms in children and adolescents was strongly linked to the family’s level of functioning [
12]. Likewise, in a clinical sample of 12–17 year-olds being treated for somatic symptoms over a 12-month period, Hoffman et al. found that family functioning was strongly associated with psychosocial functioning [
13]. Rhee et al. found that a lack of parental affection, involvement and control was linked to somatic complains among American adolescents in grades 7 to 12 [
14]. However, an association between poor family functioning and later development of somatic symptoms has not previously been documented in a non-clinical sample of Danish adolescents.
Previous studies also demonstrate that parents’ own physical and mental health complaints are associated with increased levels of physical symptoms among their children [
12]. Craig et al. found that the health anxieties of somatizing mothers are reflected in their children, who are more likely to have concerns about their own health [
15], but these results are based on cross-sectional data and only include information about somatic symptoms of one of the parents. A UK population-based birth cohort study confirms and expands on these findings, documenting that childhood experience of illness in parents is an independent risk factor for later somatic symptoms [
16]. Other negative life events such as parental divorce, parental illness or death are likewise found to be associated with an increased level of somatic symptoms [
17,
18], but these findings do not take into account other negative childhood conditions, such as poor family function or somatic symptoms of the parents.
A review from 2011 by Schultze and Petermann identified the following family risk factors for the development of somatic symptoms: somatic symptoms of parents, psychopathology or disease of a close family member, dysfunctional family climate, traumatic experiences in childhood and insecure attachment [
19]. However, only one of the studies included in the review used a prospective design, while the rest of the studies used cross-sectional or retrospective designs. As such, the review identifies a lack of prospective studies that investigate negative childhood conditions in relation to somatization and that take into account other risk factors.
In this study, we expand on previous research by including prospectively collected information about somatic symptoms from both parents and negative childhood conditions as well as information about somatic symptoms of the participant at two separate age points (early and late adolescence). By doing so, we aim to provide more precise and detailed information about the intergenerational transmission of somatic symptoms in a healthy population and to help school and health professionals detect adolescents with somatic symptoms before these symptoms develop into more persistent symptoms or serious health problems.
Aim
This study aims to investigate whether somatic symptoms of the participants’ parents, poor family functioning, or negative life events during childhood (up to age 15) result in somatic symptoms in early adolescence (age 15) or late adolescence (age 18).
Results
As shown in Table
1, a higher proportion of girls reported many somatic symptoms at ages 15 and 18 (39 and 34% respectively) compared with boys (19 and 16% respectively). Approximately 13% of all participants had experienced two or more negative life events at age 15; this applied slightly more to girls than boys (14% vs. 12%), but no significant gender differences were found in relation to the distribution of any of the independent variables.
The associations between the socioeconomic variables and somatic symptoms at ages 15 or 18 were not statistically significant, including the association between parental education and somatic symptoms at age 18 (fully adjusted: RR 1.19, 95%-CI, 0.74–1.89 and RD 5, 95%-CI, − 8-17%).
As shown in Table
2, the childhood conditions showing statistically significant associations with somatic symptoms of all the participants at age 15 were poor family functioning (fully adjusted: RR 1.75, 95%-CI, 1.43–2.14 and RD 18, 95%-CI, 11–25%) and having experienced two or more negative life events (fully adjusted: RR 1.73, 95%-CI, 1.31–2.28 and RD 24, 95%-CI, 11–37%). For boys experiencing poor family function, the risk of developing somatic symptoms was approximately 2.5 times higher than boys from well-functioning families, and 33% more boys from poor-functioning families reported somatic symptoms than boys from well-functioning families (results not shown). Somatic symptoms of the mother showed an association with self-reported somatic symptoms at age 15 for the whole sample (fully adjusted: RR 1.25, 95%-CI, 1.03–1.52 and RD 8, 95%-CI, 2–13%) and in girls (fully adjusted: RR 1.45, 95%-CI, 1.21–1.74 and RD 15, 95%-CI, 6–24%).
As shown in Table
3, the childhood conditions showing significant associations with somatic symptoms of all participants at age 18 were somatic symptoms of the father (fully adjusted: RR 1.35, 95%-CI, 1.04–1.74 and RD 7, 95%-CI, 0.9–14%) and poor family functioning (fully adjusted: RR 1.32, 95%-CI, 1.00–1.75 and RD 7, 95%-CI, 0.2–14%). Family functioning showed a significant association with somatic symptoms at age 18 among the girls (fully adjusted: RR 1.71, 95%-CI, 1.32–2.21 and RD 14, 95%-CI, 3–25%).
Discussion
In this study, we found statistically significant associations between experiencing poor family functioning and reporting somatic symptoms at ages 15 or 18, when adjusted for other childhood risk factors. The relative risks were 2.5 for the boys at age 15 and 1.71 for the girls at age 18. Negative life events up to the age of 15 showed a significant association with reporting somatic symptoms at age 15, but the association was not significant at age 18. No relative risks above 1.35 were found between parents reporting somatic symptoms and the participants reporting somatic symptoms at ages 15 or 18.
To our knowledge, this is the first prospective study that examines the associations between several negative childhood conditions, including somatic symptoms of the parents and reporting of somatic symptoms in adolescence in a population-based sample.
Poor family functioning showed a significant association with somatic symptoms at age 15 and 18. These findings are in line with the results of previous studies [
14,
32,
33]. In a Swedish cohort, Landstedt et al. found that poor parental and peer relationships at age 16 continued to be associated with functional somatic health symptoms for up to 26 years [
32], and a cross-sectional study by Hart et al. found that family conflict was associated with clinically significant somatic complaints reported by elementary school children [
33]. However, the latter study included data from a predominantly African American urban study population, which may limit the ability to generalize the findings to a Danish population. The results of this study show that social workers and teachers in contact with adolescents should be aware of the adolescents’ family situation if they wish to prevent the development of somatic symptoms.
In line with earlier findings, we found that somatic symptoms of the parents was associated with somatic symptoms of the children [
19,
34]. However, at both age 15 and 18, the relative risks were not above 1.35. A study by Janssens et al. found that 11–16 year-olds whose parents reported high rates of functional somatic symptoms were more than four times as likely to report persistent functional somatic symptoms [
34]. Our study did not find such a strong association, which is perhaps because we did not measure persistent symptoms and thus most likely measured less chronic conditions. Another study by Craig et al. found that children of somatizing mothers were more likely to experience emotional or behavioral problems, have greater concerns about their own health, and have higher consultation rates for functional somatic symptoms [
15]. In our study, we used self-reported information about somatic symptoms of both the mother and the father. To our knowledge, such detailed cross-generational information about somatic symptoms has not yet been reported. It seems that having a somatizing mother increases the risk of girls having somatic symptoms at age 15. Somatic symptoms of the father were associated with somatic symptoms of their children at age 18 and the estimates where relatively robust to adjustments.
Earlier prospective studies have shown that negative life events in childhood are associated with somatic symptoms in adolescence in both genders [
16‐
18,
35] and in girls only [
36], but this has not previously been documented in a Danish population of young people. In our study, the association between negative life events and somatic symptoms was significant at age 15, whereas the association was not significant at age 18. It is possible that the association would have been significant if some of the questions regarded negative life events of a more serious nature. For example, as mentioned above, one of the questions regarded divorce of the parents, which does not identify an uncommon life event in Denmark.
In this study, the outcome was measured at the two ages 15 and 18. We consider these ages relevant for measuring somatic symptoms in early and late adolescence, because they represent particularly sensitive life periods [
37].
This study has several strengths, including its longitudinal design and relatively large sample size. Moreover, the study examines a population-based sample, which increases the generalizability of its results. Another strength is that data about somatic symptoms were available from participants at both ages 15 and/or 18 and from both of their parents, which allowed us to examine the course of somatic symptoms throughout adolescence and to differentiate between somatic symptoms of the father and the mother. Finally, the use of both register and questionnaire data minimizes the risk of common method variance and thereby the risk of bias [
38].
Some limitations of the study also have to be taken into account. Despite the large sample size, the group of participants with complete information about outcome and all exposures was only n = 1073 (36%) and n = 895 (38%) at age 15 and 18 respectively. This was primarily due to missing information about father’s somatic symptoms. A supplementary analysis was performed to investigate how the estimates changed if only those who had answered information about somatic symptoms at both age points were included. The most significant change in estimate was seen in relation to negative life events and somatic symptoms at age 15, where the complete case analysis increased the relative risk by 0.24 and the risk difference by 7%. All other estimates showed inconsiderable changes.
Another limitation was the use of different items when generating the somatic symptoms scales at age 15 and 18. Although the two scales contained five of the same items, it is a limitation of the study that the number of items, and thus symptoms asked about, was different at the two age collection points. Supplementary analyses showed that when using only the five identical items both at age 15 and 18 only minor changes were seen. The biggest change in estimate was a decrease of 0.25 in relative risk.
It would have been possible to use another instrument to measure negative life events, such as the ACE questionnaire, though many of the items in the ACE questionnaire are similar to those used in this study [
39].
Since information about family functioning and somatic symptoms at age 15 was collected at the same time point, it is possible that negative affectivity could have played a role. In other words, it is possible that poor family functioning influences the way an individual perceives and reports his/her current symptoms, meaning that those adolescents in our study who reported poor family functioning could have automatically reported more somatic symptoms. This problem could potentially have led to differential misclassification and an overestimation of the association between family functioning and somatic symptoms. However, since this study shows associations between family functioning at age 15 and the reporting of somatic symptoms both at age 15 and 18, this potential bias is most likely limited. Another limitation of the study is that it was not possible to adjust for chronic illness among the participants. It is possible that the reported symptoms were caused by some kind of chronic illness. However, chronic illness would most likely be associated with the outcome and not the exposures and would therefore not lead to differential misclassification [
40].
In prospective cohort studies, there will always be some selection based on participation, but, when comparing parental income and educational level of the source population and the study population, only small differences were seen. The prevalence of families from the lowest percentile decreased from 33 to 30%, and families with less than 10 years of education decreased from 14 to 12.5%. Information about somatic symptoms was only available for approximately half of the fathers. If the father’s participation was related to both his own somatization and the degree of somatic symptoms of the child, this could potentially have biased the risk estimates. When comparing the prevalence of somatic symptoms among those children whose fathers responded and those children whose fathers did not respond, we only found minor differences in the two groups corresponding to 28 and 30%, respectively.
A previous study on the Vestliv Cohort found that selection due to participation does not necessarily significantly influence the risk estimates measured [
41]. Therefore, the potential selection bias is most likely minor.
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