Author Affiliations: The Generation R Study Group (Ms Verlinden and Drs Jaddoe and Guxens), the Department of Child and Adolescent Psychiatry, Sophia Children's Hospital (Ms Verlinden and Drs Tiemeier, Hudziak, Verhulst, and Jansen), and the Departments of Epidemiology (Drs Tiemeier, Jaddoe, and Hofman), Psychiatry (Dr Tiemeier), Pediatrics (Dr Jaddoe), and Public Health (Dr Raat), Erasmus University Medical Center, Rotterdam, and Department of Biological Psychology, Vrije Universiteit, Amsterdam (Dr Hudziak), the Netherlands; Departments of Psychiatry, Medicine, and Pediatrics, College of Medicine, University of Vermont, Burlington (Dr Hudziak); and Center for Research in Environmental Epidemiology–Hospital del Mar Research Institute, Barcelona, Catalonia, Spain (Dr Guxens).
Objective To determine whether the amount, type, and patterns of television viewing predict the onset or the persistence of externalizing problems in preschool children.
Design Longitudinal study of a prospective population-based cohort in the Netherlands.
Setting Parents reported time of television exposure and type of programs watched by children. Externalizing problems were assessed using the Child Behavior Checklist at 18 and 36 months.
Participants A population-based sample of 3913 children.
Main Exposure Television viewing time, content, and patterns of exposure (at 24 and 36 months) in children with and without preexisting problems to assess the incidence and persistence of externalizing problems.
Main Outcome Measures Externalizing problems at 36 months.
Results Program content and time of television exposure assessed at 24 months did not predict the incidence of externalizing problems at 36 months (odds ratio, 2.24; 95% CI, 0.97-5.18). However, the patterns of exposure over time reflecting high levels of television viewing were associated with the incidence of externalizing problems (odds ratio, 2.00; 95% CI, 1.07-3.75) and the persistence of the preexisting externalizing problems (2.59; 1.03-6.55).
Conclusions Our study showed that high television exposure increases the risk of the incidence and the persistence of externalizing problems in preschool children.
According to the recently updated guidelines of the American Academy of Pediatrics,1 media exposure at a young age should be discouraged because it may have negative consequences for the health and development of children. It has been reported that 17% to 48% of children aged 3 years or younger do not comply with these recommendations.2 A study of media consumption in the United States has demonstrated that 73% of preschool children watch television (TV) on a daily basis, spending approximately 2 hours a day in front of TV.3 Increased media exposure time among young children,4,5 a shift toward younger age,2,3,6 and exposure to adult content6 reflect the importance of this public health problem.
Exposure to media encompasses both viewing time and the content of the media.7- 10 Several studies showed positive effects of educational content on a number of developmental outcomes.7,11,12 However, there is also evidence suggesting an association between exposure time and behavioral outcomes regardless of the content.13,14 Negative effects of excessive TV viewing and its content were reported in particular for aggressive behavior13,15- 20 and attention problems.5,15- 17 However, these studies were conducted mostly in school-aged children and adolescents, whereas aggressive behavior and attention problems, which are well-known risk factors for a number of disorders, are already prevalent in early childhood.18 Poor attention ability and aggression in children are referred to as externalizingproblems. The term also refers to such behaviors as noncompliance, hyperactivity, and concentration difficulties.18- 20
Currently, despite the high prevalence of TV viewing among preschool children, little is known about the effects of TV exposure on subsequent externalizing problems. Several high-quality studies examined the prevalence of media exposure21 and its associations with cognitive development,22 hyperactivity-inattention, and prosocial behavior.23,24 Most studies13,25,26 of externalizing problems in preschool children, however, have limitations, such as relatively small and high-risk samples25 and cross-sectional data,13,26 which cannot establish the temporality of the observed association. Furthermore, earlier studies did not address content of TV programs watched by young children23 and did not adjust for parental psychosocial risk factors.13,23
Using prospective data from a large population-based cohort in the Netherlands, we addressed the following questions: (1) Is the duration and content of TV exposure at 24 months associated with externalizing problems at 36 months? (2) What is the effect of the patterns of TV exposure between 24 and 36 months on incident and persistent externalizing problems at 36 months?
Compared with earlier similar research,27 we examined behavioral outcomes among children at a younger age and accounted for the preexisting problems to examine the persistence of problem behavior. Whereas most of the previous studies were conducted in the United States with high levels of TV viewing, we examined the effects of TV viewing on externalizing problems among children in Europe.
This study was performed within the Generation R Study, a large population-based cohort in Rotterdam, the Netherlands. The cohort has been described in detail elsewhere.28 The Generation R Study was approved by the Medical Ethics Committee of the Erasmus University Medical Center.
Pregnant women living in Rotterdam (delivery date of April 1, 2002, through January 31, 2006) were invited to participate. Full consent for study participation was obtained from 7295 mothers. All participants provided written informed consent. Data on children's TV exposure at 24 and 36 months were available for 4368 children. For 3913 of these children, information on externalizing problems at 18 and 36 months was available. Analyses of these 3913 children were performed in 2 strata: children without preexisting externalizing problems (n = 3437) and children with externalizing problems present at 18 months (n = 476). However, analyses of repeated measure of TV exposure patterns were performed in 3761 children (ie, in 2 strata of 3309 and 452 children from this group of 3761).
Parental questionnaires at 24 and 36 months contained questions on TV exposure of children. In a similar study using a continuous measure to assess TV viewing at 2.5 and 5.5 years, exposure was categorized as more than 2 hours of daily TV viewing.27 We used a similar categorization but the maximum duration of TV viewing at 24 months was adapted to “more than 1 hour” accounting for the younger age. Therefore, duration of daily TV viewing was assessed using the following answer categories: “never,” “less than 0.5 hour,” “0.5 to 1 hour,” and “more than 1 hour” a day. Categories at 36 months were adapted (categories “1 to 2 hours” and “more than 2 hours” were added) to differentiate at the high ranges in older children.
At 24 months, parents also reported whether their child watched TV programs suitable or unsuitable for children. In the Netherlands, TV is state regulated and is organized by channels, which have content appropriate for children (eg, cartoons and educational programs). Parents reported channels and programs their children watched, and whether their children watched programs for adults or age-inappropriate programs (the category “unsuitable-for-children TV programs”). Programs shown on the channels for children were categorized as “suitable-for-children TV programs.”
On the basis of TV exposure at 24 and 36 months, we created a variable reflecting the patterns of daily exposure over time: “never or less than 0.5 hour” (<0.5 h/d at 24 and 36 months) (n = 789), “continued low TV exposure” (0.5-1 h/d at both ages) (n = 974), “continued moderate TV exposure” (1 h/d at both ages) (n = 681), and “high exposure” (reflecting an increase in exposure and continued high exposure) (n = 1317). The size of the latter group allowed more specific exposure definitions: “increased TV exposure time” (increased from <0.5 h/d at 24 months to ≥1 h/d at 36 months) (n = 276); and “continued high TV exposure” (≥0.5 h/d at 24 months and ≥1 h/d at 36 months) (n = 1041). The 2 categories reflecting decreasing exposure were too infrequent for meaningful analyses (total n = 152 for 2 exposure categories over 2 strata); therefore, these categories were not used in further analyses. Consequently, the analyses of the patterns of TV exposure were performed in 3761 of 3913 children (ie, in 2 strata of 3309 and 452 children from this group of 3913).
The Dutch version of the Child Behavior Checklist (for children aged 1½-5 years)19,29 was used to obtain parent reports on children's behavioral problems in the preceding 2 months at 18 and 36 months on a 3-point Likert scale. The externalizing scale consists of 2 subscales: attention problems (5 items) and aggressive problems (19 items). Examples of items assessing attention and aggression problems are “Can't sit still, restless, or hyperactive” and “Hits others,” respectively. Because the distribution of the continuous variable was skewed and could not be transformed to satisfy the assumption of normality, a dichotomous variable was used. We applied a cut-off point based on Dutch norms.29 The subscale score equivalent to the Dutch norm (83rd percentile) for externalizing problems was a score of 18, which in our sample corresponded to the 88th percentile. The Child Behavior Checklist (for children aged 1½-5 years) has good reliability and validity.19,29
Confounders were considered on the basis of previous studies of TV exposure.2,5,8,17,21,27,30 Child sex, age, national origin, day care attendance, maternal and paternal age, educational level, marital status, monthly income, maternal symptoms of psychiatric disorders, parenting stress, and parity were assessed by questionnaires. National origin of a child was defined by country of birth of the parent(s) and categorized as Dutch, other Western, or non-Western.31 The highest attained educational level of the parents (4 categories) ranged from “low” (<3 years of general secondary education) to “high” (higher academic education or PhD).32 The net monthly household income comprised the categories: “less than [euro]1200” (approximately US $1500), “[euro]1200 to [euro]2000” (approximately US $1500-$2500), and “more than [euro]2000” (approximately US $2500).
The Brief Symptom Inventory, a validated instrument containing 53 self-appraisal statements,33 was used to assess general symptoms of maternal psychiatric disorders when children were 2 months old. Parenting stress was assessed by the Nijmeegse Ouderlijke Stress Index–Kort,34 a questionnaire consisting of 25 items on parenting stress related to parent and child factors. Weighted sum scores were used in the analyses. Day care attendance was categorized as “less than 16 hours per week” and “16 hours or more per week” (modal value).
Analyses were performed in 2 different strata of children. A stratum without behavioral problems at 18 months was analyzed (n = 3309), allowing us to identify incident behavioral problems at 36 months. The second stratum (n = 452) consisted of children who had developed externalizing problems by 18 months (ie, some months before TV viewing was assessed). This enabled us to determine the influence of TV exposure on persistence of behavioral problems.
First, we examined whether TV exposure time at the age of 24 months and exposure to specific content predicted behavioral problems at the age of 36 months, using logistic regression analyses. Three models were examined: (1) univariate, (2) adjusted for externalizing symptoms score at the age of 18 months using the continuous measure, and (3) additionally controlled for socioeconomic and psychosocial covariates. Next, we examined whether patterns of TV exposure from 24 to 36 months were associated with incident or persistent externalizing problems at 36 months using the same set of models.
The externalizing problems score at 36 months had a skewed distribution; it was dichotomized and analyzed with logistic regression. To control for the degree of externalizing problems at baseline, a continuous measure of externalizing problems at 18 months was used because logistic regression does not require the assumption of normality. The dichotomous measure of externalizing problems at 18 months was used to define the preexisting externalizing problems for the stratified analyses.
Missing data on covariates were estimated using multiple imputation techniques (SPSS, version 17 [SPSS, Inc]). All covariates were used to estimate missing values. The reported effect estimates are the pooled results of 30 imputed data sets.
Children with missing data on behavioral problems at 18 months and TV exposure time at 24 months were compared with those without missing information on these variables. Data were missing more often in children of non-Dutch national origin (45.8% vs 12.4%; P < .001). Mothers of children with missing data also were less educated (47.6% vs 23.8%), younger (mean difference, 1.4 years), and more often single (26.4% vs 15.6%) and had a lower income level (33.4% vs 32.1%) than mothers without missing data (P < .001 for all).
There were more boys (56.3% vs 48.4%) and more children of non-Dutch national origin (38.5% vs 28.1%) among children who had externalizing problems at 18 months (P < .001 for both) (Table 1). Mothers of children who had externalizing problems were slightly younger (30.9 vs 31.9 years), had lower educational levels (47.5% vs 37.3%) and lower household income (29.5% vs 21.7%), were more often single (13.7% vs 6.0%), and had higher scores for symptoms of psychiatric disorders (0.36 vs 0.19).
We examined the effects of TV exposure time and content at 24 months on the incidence of externalizing problems. Exposure time of more than 1 h/d did not predict the incidence of externalizing problems at 36 months (odds ratio [OR], 2.24; 95% CI, 0.97-5.18). The association was weaker once adjusted for socioeconomic and psychosocial covariates (OR, 1.53; 95% CI, 0.62-3.81). Also, watching unsuitable TV programs at 24 months was not related to the incidence of externalizing problems at 36 months (OR, 2.56; 95% CI, 0.95-6.88).
Next, we examined the association of children's patterns of TV exposure over time with the incidence of externalizing problems (Table 2). The overall high TV exposure was associated with incident externalizing problems (OR, 2.62; 95% CI, 1.48-4.66) and remained statistically significant after controlling for any preexisting externalizing symptoms and socioeconomic and psychosocial covariates (2.00; 1.07-3.75). Continued high exposure, a subgroup of children with high TV exposure, predicted incidence of externalizing problems also after full adjustment of the association (OR, 2.09; 95% CI, 1.08-4.01). The effect of the increased exposure time over time on the incidence (OR, 2.50; 95% CI, 1.15-5.41) attenuated once adjusted for externalizing symptoms at 18 months (1.90; 0.86-4.21).
We examined the effect of the patterns of TV exposure on the persistence of externalizing problems at 36 months in children who already had behavioral problems at the age of 18 months (Table 3). The variable reflecting overall high TV exposure predicted the likelihood of the persistent externalizing problems (OR, 3.24; 95% CI, 1.39-7.54) also after full adjustment for the confounders (2.59; 1.03-6.55). Again, we performed additional analyses in the subgroups. Adjusting the association between continued high exposure and persistent externalizing problems for preexisting externalizing symptoms and psychosocial covariates rendered it nonsignificant (OR, 2.13; CI, 0.82-5.51). Although few children had an increase in exposure between 24 and 36 months, the effect of increased TV viewing on the persistence of externalizing problems was strong in children with preexisting problems (OR, 5.99; 95% CI, 1.86-19.30).
Post hoc analyses of TV exposure patterns were performed for Aggression and Attention subscales. The obtained point estimates were in line with those for externalizing problems, although only the results for persistent attention problems reached statistical significance (see eTables 1-3).
Children develop their TV viewing patterns early in childhood and these patterns are likely to be sustained.2,35 We found that young children's continued exposure to TV increases their risk for incident externalizing problems, and children with preexisting externalizing problems are more likely to have persistent problems due to high (increasing) TV exposure early in childhood.
Several theories offer an explanation for the influence of media on child development. Content-based theories emphasize the importance of the quality of programs. According to these theories, children learn from the content by using cognitive and social learning mechanisms.9 However, studies regarding the learning effects of TV viewing are inconclusive and there is little evidence for beneficial outcomes in young children.1 In our study, the effect of content on development of externalizing problems was not statistically significant. However, the prevalence of exposure to an inappropriate content was low (8.4% in children with externalizing problems and 5.6% in those without); our sample may have been too small to detect an effect. Also, the measure of content may not have been sensitive enough, or mothers may have been disinclined to report their children's exposure to inappropriate content.
According to the displacement theory,9 time spent viewing TV replaces other intellectually and physically stimulating activities. Also, the rapid pace and various visual and audio effects may be too difficult for a young child to process.9 Having to process images in rapid sequence with little time to reflect on the content may have negative effects on attention abilities. In our study, a high level of exposure time was a risk factor for the onset and persistence of externalizing behaviors.
Our longitudinal study demonstrated the importance of repeated assessments of TV exposure and behavior. Sustained and excessive exposure posed a risk for development of behavioral problems in young children, and this conclusion is in line with earlier research on the topic.27 Collecting data longitudinally already at such a young age and differentiating between incident and persistent cases helps to address the issue of reverse causality. It is, however, more difficult to infer causality in the relation with persistent externalizing problems. Children may watch TV as a result of their preexisting problems.36,37 Parents could be more inclined to allow TV viewing.38 If children have behavioral problems, parents may be tempted to use TV as a babysitter to keep their child occupied.21 Nevertheless, the effects of high levels of exposure found in our study were consistent across incident and persistent externalizing problems.
Television exposure in this population was relatively low compared with the prevalence reported for children in the United States.3,5,21 Only 34% of children exceeded 1 h/d of TV viewing at 36 months, and only 7% exceeded 2 h/d at 36 months. This difference in exposure could be related to the high number of working hours of the parents or the societal attitudes about TV viewing.
Large population-based cohort studies provide an opportunity to prospectively investigate the association between TV viewing in early childhood and behavioral problems. Differentiating the effect of such exposure on the incidence and the persistence of behavioral problems helped in establishing the temporality of the association. Furthermore, all studied associations were adjusted for a large number of covariates.
The nonresponse analyses indicated possible selective nonresponse, which could have biased our results. Another limitation of our study is the use of parent-reported media exposure. Mothers could have underreported the TV exposure giving socially desired answers. Using objective and specific measures could have provided more extensive and more precise information on TV viewing behaviors among children. Several other studies have used diary methods that appear to be more accurate in measuring the exposure and its content.7,25,35,39 However, the mother's report is well correlated with the diary method.39 Another limitation of our study is the use of a categorical rather than a continuous measure of the TV time exposure. Nevertheless, previous epidemiologic studies23,40,41 of population-based samples have used similar categorical measures. Furthermore, other factors that may affect both TV viewing and externalizing problems, such as exposure to aggression or abuse in real life42,43 or temperament of a child,44,45 were not addressed. Finally, distinguishing between foreground and background exposures can advance the understanding of the mechanisms through which TV viewing affects child development.
In conclusion, preschool children are a major target audience of the TV market in Western societies.13,46 Extensive exposure to media influences development, behavior, and day-to-day activities of young children. We have demonstrated that high levels of TV exposure increase the likelihood of externalizing problems in preschool children, even in those who did not have preexisting externalizing problems. Having considered the findings of this and previous studies,2,13,16,17,26,27,47- 52 the most useful advice for parents of preschool children would be to follow the American Academy of Pediatrics guidelines1,53 and discourage young children's exposure to TV either as the main activity or as a background exposure. Perhaps in doing so not only will externalizing problems be reduced but also associated problems such as obesity54- 57 and other negative outcomes30,58- 60 may be prevented.
Correspondence: Henning Tiemeier, MD, PhD, Department of Child and Adolescent Psychiatry, Erasmus University Medical Center, PO Box 2060, 3000 CB Rotterdam, the Netherlands (firstname.lastname@example.org).
Accepted for Publication: March 7, 2012.
Published Online: August 6, 2012. doi:10.1001 /archpediatrics.2012.653.
Author Contributions:Study concept and design: Verlinden, Tiemeier, Hofman, Verhulst, and Jansen. Acquisition of data: Tiemeier, Jaddoe, Raat, Hofman, and Verhulst. Analysis and interpretation of data: Verlinden, Tiemeier, Hudziak, Jaddoe, Raat, Guxens, and Verhulst. Drafting of the manuscript: Verlinden, Tiemeier, and Hudziak. Critical revision of the manuscript for important intellectual content: Verlinden, Hudziak, Jaddoe, Raat, Guxens, Hofman, Verhulst, and Jansen. Statistical analysis: Verlinden, Jaddoe, Raat, Guxens, and Jansen. Obtained funding: Tiemeier, Jaddoe, and Hofman. Study supervision: Tiemeier, Hudziak, Hofman, Verhulst, and Jansen.
Financial Disclosure: Dr Hudziak reports that he has received funding from the National Institute of Mental Health and the National Institute of Diabetes and Digestive and Kidney Disease. His primary appointment is with the University of Vermont. He has additional appointments with Erasmus University in Rotterdam; Vrije University in Amsterdam; Dartmouth Medical School in Hanover, New Hampshire; and Avera Institute of Human Behavioural Genetics in Sioux Falls, South Dakota. Dr Verhulst reports that he is a contributing editor for the Achenbach System of Empirically Based Assessment, from which he receives remuneration.
Funding/Support: The Generation R Study is made possible by financial support from the Erasmus University Medical Center Rotterdam and the Netherlands Organization for Health Research and Development (grant ZonMW “Geestkracht” program 100001003). The present study was supported by grant 017.106.370 (NWO ZonMW VIDI) from the Netherlands Organization for Scientific Research (Dr Tiemeier) and grant 602 from the Sophia Foundation for Medical Research SSWO (Dr Jansen). The work of Ms Verlinden was supported by the grant from the Netherlands Organization for Health Research and Development (ZonMW “Geestkracht” program 100001003).
Verlinden M, Tiemeier H, Hudziak JJ, et al. Television viewing and externalizing problems in preschool children: the Generation R Study. Arch Pediatr Adolesc Med.. doi:10.1001/archpediatrics.2012.653.
eTable 1. Incident Aggressive Problems and Patterns of Television Viewing
eTable 2. Incident Attention Problems and Patterns of Television Viewing
eTable 3. Persistent Attention Problems and Patterns of Television Viewing
Verlinden M, Tiemeier H, Hudziak JJ, Jaddoe VWV, Raat H, Guxens M, Hofman A, Verhulst FC, Jansen PW. Television Viewing and Externalizing Problems in Preschool ChildrenThe Generation R Study. Arch Pediatr Adolesc Med. 2012;166(10):919–925. doi:10.1001/archpediatrics.2012.653