Somatic symptoms and internalizing problems in urban youth: a cross-cultural comparison of Czech and Russian adolescents.

Background: Although the association between somatic complaints and internalizing problems (anxiety, somatic anxiety and depression) is well established, it remains unclear whether the pattern of this relationship differs by gender and in different cultures. The aim of this study was to examine cross-cultural and gender-specific differences in the association between somatic complaints and internalizing problems in youth from the Czech Republic and Russia. Methods: The Social and Health Assessment, a self-report survey, was completed by representative community samples of adolescents, age 12-17 years, from the Czech Republic (N = 4770) and Russia (N = 2728). Results: A strong association was observed between somatic complaints and internalizing psychopathology. Although the levels of internalizing problems differed by country and gender, they increased together with and largely in a similar way to somatic complaints for boys and girls in both countries. Conclusion: The association between somatic symptoms and internalizing problems seems to be similar for boys and girls across cultures.

Irritable bowel syndrome and functional abdominal pain in five-year-old children are related to lifestyle.

AIM: Abdominal pain of functional origin is very common in childhood, and environmental factors are thought to be of aetiologic importance. The anthroposophic lifestyle has dietary and lifestyle characteristics that may influence child health, and this study aimed to assess the effect of such lifestyles on abdominal pain of functional origin. METHODS: A prospective Swedish lifestyle cohort (n = 470) was followed from birth to five years of age. Family lifestyles were characterised through questionnaires. Abdominal pain was defined as irritable bowel syndrome or functional abdominal pain according to the Rome III criteria and measured with parental questionnaires and interviews at the age of five. RESULTS: The prevalence of abdominal pain was 15%. Children were more likely to have abdominal pain at five years of age if their family had a partly anthroposophic lifestyle, with an adjusted odds ratio (OR) of 2.61 (95% CI 1.15-5.93), or an anthroposophic lifestyle, with an adjusted OR of 2.34 (95% CI 0.96-5.70). CONCLUSION: A family lifestyle with anthroposophic characteristics was associated with an increased risk of abdominal pain in five-year-old children. The mechanisms for this increase were unclear, but we speculate that there may have been different prerequisites for coping with stressors.

Does Information About Neuropsychiatric Diagnoses Influence Evaluation of Child Sexual Abuse Allegations?

This study aimed at investigating if attitudes toward children with neuropsychiatric disorders influence evaluations concerning allegations of child sexual abuse. Law students (n = 107) at Stockholm University, Sweden, were presented a transcript of a mock police interview with a girl, 11 years of age. This interview was based on a real case, selected as a "typical" example from these years concerning contributions from the interviewer and the alleged victim. After having read the transcript, the students responded to a questionnaire concerning degree of credibility, if the girl talked about events that had really occurred, richness of details, and if the narrations were considered truthful and age-adequate. Fifty-four of the students were also told that the girl had been given the diagnoses of attention deficit/hyperactivity disorder and Asperger syndrome. Students who were informed about the diagnoses gave significantly lower scores concerning credibility of the interviewee. To a lesser degree they regarded her narrations as expressions of what had really occurred and considered her statements less truthful. Furthermore, they found that the narrations contained fewer details. Finally, they found the girl less competent to tell about abuse. We conclude that a neuropsychiatric disorder may infer risks of unjustified skeptical attitudes concerning trustworthiness and cognitive capacity.

Anthroposophic lifestyle and salivary cortisol are associated with a lower risk of sensitization during childhood.

BACKGROUND: Infants from anthroposophic families have low cortisol levels and low risk of IgE-sensitization during first 2 years of life. Our aim was to study the impact of an anthroposophic lifestyle and cortisol levels at 6 months on allergy sensitization up to age 5 years. METHODS: A total of 507 families participated from maternal healthcare centers. Parental lifestyle was categorized as anthroposophic, partly anthroposophic, or non-anthroposophic. Blood samples for analyzes of sensitization were obtained from parents at inclusion and from children at 6, 12, 24, and 60 months. Salivary samples were collected at home at 6 months. RESULTS: Sensitization increased from 2.9% to 26.0% in the anthroposophic group, from 8.4% to 26.8% in the partly anthroposophic group, and from 19.1% to 44.1% in the non-anthroposophic group. Children from anthroposophic families had lower cortisol levels in the morning, afternoon, and evening. The odds ratio (OR) for anthroposophic lifestyle was always <1 and lowest at 12 months (OR, 0.10; 95% CI, 0.03-0.36). Adjusting for cortisol levels at 6 months increased these ORs at 12 and 24 months. At the same ages, ORs for sensitization were elevated also for cortisol levels at 6 months. Analyzes in children not sensitized at 6 months confirmed the cortisol-related risk of sensitization. CONCLUSIONS: Children from families with an anthroposophic lifestyle have lower risk than comparisons of developing sensitization up to 5 years. This risk is partially explained by low cortisol levels during infancy. High cortisol levels at 6 months predict sensitization up to 24 months.

Community violence exposure and severe posttraumatic stress in suburban American youth: risk and protective factors.

PURPOSE: The psychological effects of community violence exposure among inner-city youth are severe, yet little is known about its prevalence and moderators among suburban middle-class youth. This study aimed to assess the prevalence of community violence exposure among suburban American youth, to examine associated posttraumatic stress and to evaluate factors related to severe vs. less severe posttraumatic stress, such as co-existing internalizing and externalizing problems, as well as the effects of teacher support, parental warmth and support, perceived neighborhood safety and conventional involvement in this context. METHOD: Data were collected from 780 suburban, predominantly Caucasian middle-class high-school adolescents in the Northeastern US during the Social and Health Assessment (SAHA) study. RESULTS: A substantial number of suburban youth were exposed to community violence and 24% of those victimized by community violence developed severe posttraumatic stress. Depressive symptoms were strongly associated with higher levels and perceived teacher support with lower levels of posttraumatic stress. CONCLUSION: Similar to urban youth, youth living in suburban areas in North American settings may be affected by community violence. A substantial proportion of these youth reports severe posttraumatic stress and high levels of comorbid depressive symptoms. Teacher support may have a protective effect against severe posttraumatic stress and thus needs to be further assessed as a potential factor that can be used to mitigate the detrimental effects of violence exposure.

Polymorphisms in the FK506 binding protein 5 gene are associated with attention deficit hyperactivity disorder and diurnal cortisol levels.

AIM: Previous studies have shown an association between childhood attention deficit hyperactivity disorder (ADHD) and a down-regulated hypothalamus-pituitary-adrenal axis (HPA axis) with low diurnal cortisol levels. Given the role of the FK506 binding protein 5 (FKBP5) as an important regulator of the negative feedback system of the HPA axis, we set out to investigate possible associations between single nucleotide polymorphisms (SNPs) in FKBP5 in relation to ADHD and diurnal cortisol levels. METHODS: Children with ADHD (n = 81) and healthy comparisons (n = 88) collected saliva four times during a regular school day for radioimmunoassay analysis of cortisol and for genotyping of five SNPs in FKBP5 (rs9296158, rs1360780, rs9470080, rs7748266 and rs9394309). RESULTS: We found associations between SNP genotypes and ADHD as well as between genotypes and diurnal cortisol levels. One of these SNPs, rs9470080, was significantly associated with both ADHD and lower cortisol levels. CONCLUSION: This study contributes to previous findings on a down-regulated HPA axis in children with ADHD by demonstrating an association between ADHD, lower cortisol levels and SNPs of the FKBP5-gene. The relevance of these findings for the development and shaping of ADHD symptoms needs to be approached in larger samples, preferably also taking stress reactivity into consideration.

Depressive symptoms, anxiety and academic motivation in youth: Do schools and families make a difference?

This longitudinal study aimed to examine the association between depressive and anxiety symptoms and academic motivation by gender, and whether positive school and family factors would be associated with academic motivation, in spite of the presence of such symptoms. Study participants were predominantly economically disadvantaged youths aged 13-15 years in a Northeastern US urban public school system. The Social and Health Assessment (SAHA) served as the basis for a survey undertaken in 2003 and 2004 with information being used from students who participated at both time points (N = 643). Multiple linear regression analyses showed that depressive symptoms were negatively associated with academic motivation, while anxiety was positively related to academic motivation in both genders. Teacher support, school attachment and parental control were positively related to academic motivation even in the presence of internalizing problems. The negative association of depressive symptoms with academic motivation may be potentially decreased by attachment to school.

Positive versus negative mental health in emerging adulthood: a national cross-sectional survey.

BACKGROUND: The dual continuum model suggests that positive mental health not only implies the absence of mental illness, but also constitutes an entity of its own. Measures that encompass both positive and negative mental health in young adults are rare. Thus, we assessed whether dimensions corresponding to positive and negative mental health could be identified in a sample of young individuals. Additionally, we explored how such dimensions were associated with potential health-related factors. METHODS: We obtained data from the Swedish National Public Health Survey 2004-2009 (23,394 women, 18,274 men, aged 16-29 years). We used exploratory factor analysis (EFA) to identify relevant factors revealed by the 12-item General Health Questionnaire (GHQ-12) and confirmatory factor analysis (CFA) to verify the factor structure. We tested the significance of the difference between effects of potential health-related factors on positive mental health (PMH) and negative mental health (NMH). RESULTS: The EFA for the GHQ-12 revealed a two factor model with negative items that had high positive loadings on one factor and lower negative loadings on the other factor. The positive items had loading trends that were opposite those of the negative items. The fit of this model was supported by the CFA, which yielded a significantly better match than a unidimensional model. When we investigated the associations between GHQ-scores and potential predictors of health, we found that most potential predictors had significant and opposing effects on both PMH and NMH; with the strongest effects from suicidal ideation and perceived humiliation. CONCLUSIONS: Our results could be seen to indicate that positive and negative mental health are distinct and complementary constructs. Still, the results of our factor analysis may specifically reflect the wording of the items. We conclude that the GHQ-12 is an appropriate tool for its original purpose, to detect "psychiatric morbidity". More refined measures, including predictors of health, are needed to assess PMH and validate the bidimensionality hypothesis.

Risk and protective factors for peer victimization: a 1-year follow-up study of urban American students.

This study examined whether internalizing problems, parental warmth and teacher support were associated with adolescents' experience of future peer victimization in school. Data were drawn from two rounds of the longitudinal Social and Health Assessment (SAHA). Study subjects comprised 593 US urban adolescents (aged 13.8 ± 0.8 years; 56 % female). Results showed that there was a substantial degree of continuity in peer victimization over a 1-year period. The presence of internalizing (anxiety, depressive and somatic) symptoms at baseline was associated with an increased risk of peer victimization over time. Both parental warmth and teacher support were uniquely associated with a lower risk for peer victimization. Implications of these findings for prevention efforts are discussed.

The effect of violent and nonviolent video games on heart rate variability, sleep, and emotions in adolescents with different violent gaming habits.

OBJECTIVE: To study cardiac, sleep-related, and emotional reactions to playing violent (VG) versus nonviolent video games (NVG) in adolescents with different gaming habits. METHODS: Thirty boys (aged 13-16 years, standard deviation = 0.9), half of them low-exposed (≤1 h/d) and half high-exposed (≥3 h/d) to violent games, played a VG/NVG for 2 hours during two different evenings in their homes. Heart rate (HR) and HR variability were registered from before start until next morning. A questionnaire about emotional reactions was administered after gaming sessions and a sleep diary on the following mornings. RESULTS: During sleep, there were significant interaction effects between group and gaming condition for HR (means [standard errors] for low-exposed: NVG 63.8 [2.2] and VG 67.7 [2.4]; for high-exposed: NVG 65.5 [1.9] and VG 62.7 [1.9]; F(1,28) = 9.22, p = .005). There was also a significant interaction for sleep quality (low-exposed: NVG 4.3 [0.2] and VG 3.7 [0.3]); high-exposed: NVG 4.4 [0.2] and VG 4.4 [0.2]; F(1,28) = 3.51, p = .036, one sided), and sadness after playing (low-exposed: NVG 1.0 [0.0] and VG 1.4 [0.2]; high-exposed: NVG 1.2 [0.1] and VG 1.1 [0.1]; (F(1,27) = 6.29, p = .009, one sided). CONCLUSIONS: Different combinations of the extent of (low versus high) previous VG and experimental exposure to a VG or an NVG are associated with different reaction patterns-physiologically, emotionally, and sleep related. Desensitizing effects or selection bias stand out as possible explanations.

Factors influencing the prosecution of child physical abuse cases in a Swedish metropolitan area.

AIM: To examine whether case characteristics of alleged child physical abuse, such as severity, influence criminal investigation procedures and judicial outcomes. METHOD: We identified all police-reported cases of nonfatal child physical abuse during 2006 in a Swedish metropolitan area (n = 158). Case characteristics were abstracted from police records. RESULTS: Over half (56%) of the victims were boys, and the median age group was 9-12 years. The severity of the alleged violence was low in 8% of cases, moderate in 51% and high in 41%. Suspects were interviewed in 53% of cases, with fathers more likely to be interviewed than mothers. Children were forensically interviewed in 52% of cases, with 9% physically examined by a clinician and 2.5% by a forensic specialist. Seven per cent of the cases were prosecuted and 1.3% resulted in summary punishment. We found no association between severity of alleged abuse and whether the suspect was interviewed, the child was forensically interviewed or physically examined or whether the perpetrator was prosecuted. CONCLUSION: Despite the high severity of alleged violence, physical examination rates were low, suggesting a need for criminal investigative procedures on child physical abuse to be reviewed in Sweden.

Parental Sense of Coherence in the first 2 years of life is not related to parental and child diurnal cortisol rhythm or proxies of anthroposophic lifestyle.

AIM: Sense of Coherence (SOC) is hypothesized to have direct physiological consequences on endocrine and immunological processes. In this study, we compare parental SOC scores from pregnancy in groups of infants and parents representing different lifestyles (anthroposophic, partly anthroposophic and nonanthroposophic). We also analyse whether these could predict cortisol levels of the parents and their infants at 6-24 months postpartum. METHODS: Parental SOC-13 was collected during the third trimester of pregnancy from a birth cohort of families with different lifestyles. Salivary samples were collected from the whole family when the child was 6 months (n = 210), 12 (n = 178) and 24 months of age (n = 149), and cortisol levels were analysed with radioimmunoassay technique. RESULTS: Sense of Coherence scores did not differ between the three lifestyle groups, and there were no correlations between SOC scores and salivary cortisol concentrations in separate analyses of mothers, fathers and children at any sampling age or at any sampling time during the day (morning, afternoon, bedtime). CONCLUSION: Sense of Coherence scores did not vary in parents with different lifestyles and were not associated with salivary cortisol levels in parents or in children.

Early psychosocial adversity and cortisol levels in children with attention-deficit/hyperactivity disorder.

Previous studies suggest a different regulation of the hypothalamus-pituitary-adrenal axis (HPA-axis) with lower diurnal cortisol levels, especially in the morning, in children with attention-deficit/hyperactivity disorder (ADHD) compared with controls. Since exposure to foetal and childhood psychosocial adversity has been associated with both ADHD and HPA-axis functioning, such exposures may explain these low cortisol levels in ADHD via early programming of the HPA-axis. Thus, our main aim was to retrospectively study foetal and early childhood exposures to psychosocial adversity in children with ADHD and to relate these exposures to cortisol levels. Saliva samples were collected during a regular weekday in children, 6-17 years old, with clinically confirmed ADHD (n = 197) and non-affected comparisons (n = 221) for radioimmunoassay analysis of cortisol. Parental rating scales were used for categorising subtypes of ADHD and degree of exposure to adversity. Children with ADHD had more reports of at least one rated foetal adversity (p = 0.041) and childhood adversity (p < 0.001) than comparisons. The association between low morning cortisol levels and ADHD-symptoms remained when analyses were adjusted for adversities, age, sex, sampling time and symptoms of oppositional defiant disorder. No relation was found between exposures to foetal/childhood adversity and cortisol levels except for a positive relation between childhood adversity and cortisol morning increase in children with ADHD. The hypothesis that early adversity may influence the HPA-axis, leading to lower cortisol levels in children with ADHD, was not supported by our findings.

Daily life impact of malocclusion in Swedish adolescents: a grounded theory study.

OBJECTIVE: To explore how malocclusions affect daily life in adolescents and how adolescents cope with malocclusion-related distress. MATERIALS AND METHODS: Twelve strategically selected teenagers, seven girls and five boys aged 13-14 years, participated in this study. Open, tape-recorded in-depth interviews based on Focus Group Discussions (FGD) were performed using a theme guide and analyzed according to the qualitative method of classic grounded theory (GT). RESULTS: A core category was identified and named 'Repeatedly reminded of the malocclusion'. Associated to the core category, five categories were generated and labeled 'Being directed by the media's ideal image', 'Monitoring others' teeth', 'Struggling with low self-esteem', 'Hiding one's teeth' and 'Striving for cure'. Low self-esteem appeared to be frequently reinforced through the concerns for the malocclusion and handled via different coping strategies, such as hiding the teeth and striving to receive orthodontic treatment. Such processes were further enforced through the influence of media. Low self-esteem could be associated to a visible malposition of teeth, according to the informants. Having to wait for orthodontic treatment was frustrating the adolescents. CONCLUSIONS: Adolescents with malocclusion are often reminded of their condition, which can lead to avoiding strategies to minimize the negative feelings associated with the teeth and low self-esteem. Clinicians may therefore need to be aware of potential irrational behaviors when interacting with adolescents with malocclusions. The findings also suggest that there might be a discrepancy of attitudes between professionals focusing on oral health aspects of malocclusions and the adolescents focusing on esthetic aspects.

A national cohort study of parental socioeconomic status and non-fatal suicidal behaviour--the mediating role of school performance.

BACKGROUND: A link between low parental socioeconomic status and mental health problems in offspring is well established in previous research. The mechanisms that explain this link are largely unknown. The present study investigated whether school performance was a mediating and/or moderating factor in the path between parental socioeconomic status and the risk of hospital admission for non-fatal suicidal behaviour. METHODS: A national cohort of 447 929 children born during 1973-1977 was followed prospectively in the National Patient Discharge Register from the end of their ninth and final year of compulsory school until 2001. Multivariate Cox proportional hazards and linear regression analyses were performed to test whether the association between parental socioeconomic status and non-fatal suicidal behaviour was mediated or moderated by school performance. RESULTS: The results of a series of multiple regression analyses, adjusted for demographic variables, revealed that school performance was as an important mediator in the relationship between parental socioeconomic status and risk of non-fatal suicidal behaviour, accounting for 60% of the variance. The hypothesized moderation of parental socioeconomic status-non-fatal suicidal behaviour relationship by school performance was not supported. CONCLUSIONS: School performance is an important mediator through which parental socioeconomic status translates into a risk for non-fatal suicidal behaviour. Prevention efforts aimed to reduce socioeconomic inequalities in non-fatal suicidal behaviour among young people will need to consider socioeconomic inequalities in school performance.

Educational achievement and vocational career in twins - a Swedish national cohort study.

AIM: To investigate how being born and raised as a twin is associated with IQ, educational achievement and vocational career. METHODS: Register study in a national birth cohort, complemented with a siblings study. The study population included 13,368 individuals born and raised as twins and 837,752 singletons, including 3019 siblings of twins, in the Swedish birth cohorts of 1973-1981. Our outcome measures were mean grade points on a five point scale from ninth grade of primary school at 15-16 years, IQ tests on a nine grade point scale from male conscripts at 18-19 years, highest completed education, disability benefits, work income and employment at 27-35 years of age. RESULTS: Twins had slightly better mean grade point averages in ninth grade; +0.08 (95% CI 0.04-0.11) and more often had completed a university education in young adulthood; OR 1.16 (1.02-1.21) compared with singleton siblings, despite male twins having a slightly lower IQ at military conscription compared with male singletons. Employment rates, mean income and disability benefits were similar in twins and singletons. CONCLUSIONS: Twins have slightly better educational careers and similar vocational careers compared with those born as singletons.

Lifestyle and salivary cortisol at the age of 12 and 24 months.

AIM: To analyse salivary cortisol levels in 12- and 24-month-olds from families with an anthroposophic lifestyle and comparisons ('partly anthroposophic' and 'non-anthroposophic'). METHODS: Salivary samples were collected at child ages of 12 (n = 178) and 24 (n = 149) months. Cortisol was analysed with radioimmunoassay technique. RESULTS: Evening cortisol levels in children from anthroposophic families were lower than in comparisons at 12 months of age (geometric means: anthroposophic 1.7, partly anthroposophic 1.9, non-anthroposophic 3.6 nmol/L; p = 0.024) and at 24 months of age (1.1, 1.8 and 2.9 nmol/L, respectively; p = 0.002). At 24 months of age, similar differences were noted also for the afternoon levels (2.3, 3.3 and 3.9 nmol/L, respectively; p = 0.043). At age 12 months, the differences in the evening cortisol were statistically explained by a meat-free diet and at age 24 months by the anthroposophic lifestyle as such. The circadian variations were parallel in the three groups at age 12 and 24 months. No cortisol differences were observed between parents representing different lifestyles. CONCLUSIONS: An anthroposophic lifestyle is associated with low cortisol levels in the evening at age 12 and 24 months, at age 24 months also in the afternoon.

Salivary cortisol levels and allergy in children: the ALADDIN birth cohort.

BACKGROUND: Pre- and postnatal stress have been related to allergy in children, but evidence from prospective studies is limited. Several environmental factors can influence the salivary cortisol level, which is used as a measure of activity of the hypothalamic-pituitary-adrenal axis. OBJECTIVE: The aim of this study was to assess the association between salivary cortisol levels at 6 months of age and allergic manifestations during the first 2 years of life. METHODS: Salivary samples for the analysis of cortisol level were collected at 6 months of age on 3 occasions during 1 day from 203 children. Blood samples were collected at 6, 12, and 24 months of age for analyses of specific IgE. Information on allergy-related symptoms was obtained by repeated examinations of the children. Generalized estimating equation statistics were used to calculate the overall risk for outcome measures. RESULTS: The adjusted odds ratio for the relationship between morning cortisol level and IgE sensitization was 1.60 (95% CI, 1.22-2.10, P = .001) and for eczema it was 1.28 (95% CI, 1.03-1.59, P = .026). The odds ratio for afternoon cortisol level in relation to sensitization and eczema was 1.56 (95% CI, 1.26-1.94, P < .001) and 1.33 (95% CI, 1.12-1.58, P = .001), respectively, and for evening cortisol level it was 1.49 (95% CI, 1.22-1.83, P < .001) and 1.37 (95% CI, 1.18-1.59, P < .001). Salivary cortisol level in the evening was associated with food allergy. CONCLUSION: The association between salivary cortisol levels in infancy and allergic sensitization and allergic symptoms suggests a role of an altered hypothalamic-pituitary-adrenal axis in the etiological process of allergies.

Sexual abuse allegations by children with neuropsychiatric disorders.

All Swedish court cases from 2004 and 2006 concerning alleged child sexual abuse (sexual harassment excluded) were identified through criminal registers. Fourteen cases (one boy) concerned a child with a neuropsychiatric disorder. The diagnostic groups were mental retardation (10 cases), autism (three cases), and ADHD (one case). Psychiatric experts were engaged in only two cases. When experts were involved, the courts focused on credibility issues. When the courts applied neuropsychiatric arguments in the absence of an expert, they used developmental arguments. When the authors found that significant neuropsychiatric issues were not discussed by the court it concerned interpretations of symptoms and developmental standpoints. The results illustrate the complexity and pitfalls of drawing conclusions about associations between symptoms and personality characteristics on one side and accuracy of sexual abuse allegations on the other. Moreover, the results highlight the importance of a high quality system for providing courts with adequate neuropsychiatric knowledge.

ADHD after fetal exposure to maternal smoking.

INTRODUCTION: Smoking during pregnancy has been reported to be associated with a twofold to fourfold increased risk of attention-deficit hyperactivity disorder (ADHD) in the offspring. Genetic and socioeconomic confounders may contribute to this association. The aim of this study was to investigate the association between fetal exposure to maternal smoking during pregnancy and ADHD, taking such potential confounders into consideration. METHODS: A register study in a population of 982,856 children, 6-19 years of age, born at term, and residents in Sweden in 2006 was conducted. Logistic regression was used to calculate odds ratios (ORs) of maternal smoking habits during pregnancy on ADHD medication in the 927,007 study subjects where maternal smoking habits were available from the Medical Birth Register in the presence of socioeconomic and parental psychiatric morbidity confounders. To adjust the analysis also for genetic confounding, we used a within-mother between-pregnancy approach in offspring of 26,292 mothers with inconsistent smoking habits (smoking/non-smoking) between pregnancies. RESULTS: The OR for ADHD medication in offspring of mothers who smoked >or=10 cigarettes/day was 2.86 (2.66-3.07) in the entire study population after adjustment for sex and age, while this same exposure yielded an OR of only 1.26 (0.95-1.58) when two pregnancies of the same mother were analyzed in a within-subjects design. DISCUSSION: Smoking during pregnancy has a strong association with ADHD in the offspring in the general Swedish population, but this risk is primarily explained by genetic and socioeconomic confounding.