The genetics of autism spectrum disorders and related neuropsychiatric disorders in childhood

OBJECTIVE

Autism spectrum disorders are considered to be among the most heritable mental disorders, a notion based on surprisingly sparse data from small clinical studies. Population-based studies of the heritability of other neuropsychiatric disorders and comorbidities among them have also been sparse. The authors sought to address both of these issues.

METHOD

Parents of all Swedish 9- and 12-year-old twin pairs born between 1992 and 2000 (N=10,895) were interviewed regarding autism spectrum disorders and associated conditions (response rate, 80%). Concordance rates and structural equation modeling were used for evaluating causes for familial aggregation and overlap between conditions.

RESULTS

Monozygotic twins had higher concordance rates than dizygotic twins for autism spectrum disorders, attention deficit hyperactivity disorder (ADHD), developmental coordination disorder, and tic disorder. Genetic effects accounted for 80% (95% CI=29-91) of the variation in liability for autism spectrum disorders, 79% (95% CI=61-88) for ADHD, 70% (95% CI=35-83) for developmental coordination disorder, and 56% (95% CI=37-68) for tic disorder. Among monozygotic co-twins of children with autism spectrum disorders, the probability of having a diagnosis of ADHD was 44%, compared with 15% for dizygotic co-twins. Differences in cross-disorder effects between monozygotic and dizygotic twins were observed for most other comorbidities, and substantial proportions of the genetic variance for autism spectrum disorders was shared with each of the other disorders.

CONCLUSIONS

Different neuropsychiatric disorders seem to have a common genetic etiology, suggesting caution in the use of diagnostic entities and proband status in efforts to uncover genes predisposing to autism spectrum disorders.

The Swedish Twin Registry in the Third Millennium: An Update

The Swedish Twin Registry was first established in the late 1950s. Today it includes more than 170,000 twins — in principle all twins born in Sweden since 1886. In this article we describe some ongoing and recently completed projects based on the registry. In particular, we describe recent efforts to screen all twins born between 1959 and 1985, and young twin pairs when they turn 9 and 12 years of age. For these studies, we present initial frequencies of common conditions and exposures.

The Child and Adolescent Twin Study in Sweden (CATSS)

The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study targeting all twins born in Sweden since July 1, 1992. Since 2004, parents of twins are interviewed regarding the children's somatic and mental health and social environment in connection with their 9th or 12th birthdays (CATSS-9/12). By January 2010, 8,610 parental interviews concerning 17,220 twins had been completed, with an overall response rate of 80%. At age 15 (CATSS-15) and 18 (CATSS-18), twins and parents complete questionnaires that, in addition to assessments of somatic and mental health, include measures of personality development and psychosocial adaptation. Twin pairs in CATSS-9/12 with one or both twins screening positive for autism spectrum disorders, attention deficit/hyperactivity disorder, tic disorders, developmental coordination disorder, learning disorders, oppositional defiant disorder, conduct disorder, obsessive-compulsive disorder, and/or eating problems have been followed with in-depth questionnaires on family, social environment and personality, and subsequently by clinical assessments at age 15 together with randomly selected population controls, including 195 clinically assessed twin pairs from the first 2 year cohorts (CATSS-15/DOGSS). This article describes the cohorts and study groups, data collection, and measures used. Prevalences, distributions, heritability estimates, ages at onset, and sex differences of mental health problems in the CATSS-9/12, that were analyzed and found to be overall comparable to those of other clinical and epidemiological studies. The CATSS study has the potential of answering important questions on the etiology of childhood mental health problems and their role in the development of later adjustment problems.

The autism--tics, AD/HD and other comorbidities inventory (A-TAC): further validation of a telephone interview for epidemiological research

BACKGROUND

Reliable, valid, and easy-to-administer instruments to identify possible caseness and to provide proxies for clinical diagnoses are needed in epidemiological research on child and adolescent mental health.The aim of this study is to provide further validity data for a parent telephone interview focused on Autism--Tics, Attention-deficit/hyperactivity disorder (AD/HD), and other Comorbidities (A-TAC), for which reliability and preliminary validation data have been previously reported.

METHODS

Parents of 91 children clinically diagnosed at a specialized Child Neuropsychiatric Clinic, 366 control children and 319 children for whom clinical diagnoses had been previously assigned were interviewed by the A-TAC over the phone. Interviewers were blind to clinical information. Different scores from the A-TAC were compared to the diagnostic outcome.

RESULTS

Areas under ROC curves for interview scores as predictors of clinical diagnoses were around 0.95 for most disorders, including autism spectrum disorders (ASDs), attention deficit/hyperactivity disorder (AD/HD), tic disorders, developmental coordination disorders (DCD) and learning disorders, indicating excellent screening properties. Screening cut-off scores with sensitivities above 0.90 (0.95 for ASD and AD/HD) were established for most conditions, as well as cut-off scores to identify proxies to clinical diagnoses with specificities above 0.90 (0.95 for ASD and AD/HD).

CONCLUSIONS

The previously reported validity of the A-TAC was supported by this larger replication study using broader scales from the A-TAC-items and a larger number of diagnostic categories. Short versions of algorithms worked as well as larger. Different cut-off levels for screening versus identifying proxies for clinical diagnoses are warranted. Data on the validity for mood problems and oppositional defiant/conduct problems are still lacking. Although the A-TAC is principally intended for epidemiological research and general investigations, the instrument may be useful as a tool to collect information in clinical practice as well.

The Swedish Twin Registry in the third millennium: an update

The Swedish Twin Registry was first established in the late 1950s. Today it includes more than 170,000 twins--in principle, all twins born in Sweden since 1886. In this article we describe some ongoing and recently completed projects based on the registry. In particular, we describe recent efforts to screen all twins born between 1959 and 1985, and young twin pairs when they turn 9 and 12 years of age. For these studies, we present initial frequencies of common conditions and exposures.

Familial clustering of suicide risk: a total population study of 11.4 million individuals

BACKGROUND

Research suggests that suicidal behaviour is aggregated in families. However, due to methodological limitations, including small sample sizes, the strength and pattern of this aggregation remains uncertain.

METHOD

We examined the familial clustering of completed suicide in a Swedish total population sample. We linked the Cause of Death and Multi-Generation Registers and compared suicide rates among relatives of all 83 951 suicide decedents from 1952-2003 with those among relatives of population controls.

RESULTS

Patterns of familial aggregation of suicide among relatives to suicide decedents suggested genetic influences on suicide risk; the risk among full siblings (odds ratio 3.1, 95% confidence interval 2.8-3.5, 50% genetic similarity) was higher than that for maternal half-siblings (1.7, 1.1-2.7, 25% genetic similarity), despite similar environmental exposure. Further, monozygotic twins (100% genetic similarity) had a higher risk than dizygotic twins (50% genetic similarity) and cousins (12.5% genetic similarity) had higher suicide risk than controls. Shared (familial) environmental influences were also indicated; siblings to suicide decedents had a higher risk than offspring (both 50% genetically identical but siblings having a more shared environment, 3.1, 2.8-3.5 v. 2.0, 1.9-2.2), and maternal half-siblings had a higher risk than paternal half-siblings (both 50% genetically identical but the former with a more shared environment). Although comparisons of twins and half-siblings had overlapping confidence intervals, they were supported by sensitivity analyses, also including suicide attempts.

CONCLUSIONS

Familial clustering of suicide is primarily influenced by genetic and also shared environmental factors. The family history of suicide should be considered when assessing suicide risk in clinical settings or designing and administering preventive interventions.

Genetic and environmental effects on same-sex sexual behavior: a population study of twins in Sweden

There is still uncertainty about the relative importance of genes and environments on human sexual orientation. One reason is that previous studies employed self-selected, opportunistic, or small population-based samples. We used data from a truly population-based 2005-2006 survey of all adult twins (20-47 years) in Sweden to conduct the largest twin study of same-sex sexual behavior attempted so far. We performed biometric modeling with data on any and total number of lifetime same-sex sexual partners, respectively. The analyses were conducted separately by sex. Twin resemblance was moderate for the 3,826 studied monozygotic and dizygotic same-sex twin pairs. Biometric modeling revealed that, in men, genetic effects explained .34-.39 of the variance, the shared environment .00, and the individual-specific environment .61-.66 of the variance. Corresponding estimates among women were .18-.19 for genetic factors, .16-.17 for shared environmental, and 64-.66 for unique environmental factors. Although wide confidence intervals suggest cautious interpretation, the results are consistent with moderate, primarily genetic, familial effects, and moderate to large effects of the nonshared environment (social and biological) on same-sex sexual behavior.

The Swedish Twin study of CHild and Adolescent Development: the TCHAD-study

The Swedish Twin study of CHild and Adolescent Development (TCHAD) is a longitudinal study of how genes and environments contribute to development of health and behavioral problems from childhood to adulthood. The study includes 1480 twin pairs followed since 1994, when the twins were 8 to 9 years old. The last data collection was in 2005 when the twins were 19 to 20 years old. Both parents and twins have provided data. In this article we describe the sample, data collections, and measures used. In addition, we provide some key findings from the study, focusing on antisocial behavior, criminality, and psychopathic personality.

Familial factors do not confound the association between birth weight and childhood asthma

OBJECTIVE

Studies have found associations between low birth weight and asthma. However, this association could be due to familial confounding. Our objective was to investigate whether fetal growth and birth weight affect the risk of asthma in childhood, controlling for gestational age (GA), and shared (familial) environment and genetic factors.

PATIENT AND METHODS

Information on asthma, zygosity, birth characteristics, and potential confounders was collected for all 9- and 12-year-old twins through the Swedish Twin Register and Medical Birth Register. To obtain an overall effect of birth weight on risk of asthma, we performed cohort analyses on all twins (N = 10918). To address genetic and shared environmental confounding, we performed a co-twin control analysis by using the 157 monozygotic and 289 dizygotic same-sex twin pairs who were discordant for asthma.

RESULTS

The overall rate of asthma ever was 13.7%. In the cohort analysis, the adjusted odds ratio (OR) for asthma in relation to a 1000-g decrease in birth weight was 1.57 (95% confidence interval [CI]: 1.38-1.79), and for each reduced gestational week the OR was 1.10 (95% CI: 1.07-1.13). In the co-twin control analyses, a 1000-g decrease in birth weight corresponded to an OR of 1.25 (95% CI: 0.74-2.10) for dizygotic same-sex twins and 2.42 (95% CI: 1.00-5.88) for monozygotic twins.

CONCLUSIONS

There is an association between fetal growth and childhood asthma that is independent of GA and shared (familial) environment and genetic factors, which indicates that fetal growth restriction affects lung development, supporting additional studies on the early metabolic and physiologic mechanisms of childhood asthma.

Risk factors for violent crime in Schizophrenia: a national cohort study of 13,806 patients

OBJECTIVE

To determine risk factors for and prevalence of violent crime in patients with schizophrenia, and in particular, to explore the contribution of familial risk factors.

METHOD

We designed a cohort study that followed up patients with 2 or more hospitalizations for schizophrenia (ICD-8, ICD-9, and ICD-10 criteria) and investigated the risk for a violent conviction using Cox proportional hazards models. All 13,806 patients with 2 hospital discharge diagnoses of schizophrenia from January 1, 1973, through December 31, 2004, in Sweden were followed until violent conviction, emigration, death, or end of follow-up (December 31, 2004), and associations with sociodemographic, individual (substance abuse comorbidity, and previous violence), and familial (parental violent crime and parental alcohol abuse) factors were examined.

RESULTS

Over an average follow-up period of 12 years, 17.1% (N = 1519) of the men and 5.6% (N = 273) of the women with 2 or more hospitalizations for schizophrenia had a violent conviction after discharge from hospital. Familial risk factors had moderate effects, increasing the risk for violent convictions by 50% to 150%. After adjustment for sociodemographic and individual risk factors, the associations between parental violent crime and risk of violent convictions remained in men (adjusted hazard ratio [HR] = 1.65, 95% CI = 1.33 to 2.04) and in women (adjusted HR = 1.83, 95% CI = 1.11 to 3.01), whereas parental alcohol abuse was no longer significantly associated with violent crime.

CONCLUSION

Parental violent crime had moderate associations with violent crime in male and female offspring with at least 2 hospitalizations for schizophrenia, which were mostly stronger than the better documented sociodemographic risk factors. This suggests that familial (genetic or early environmental) risk factors have an important role in the etiology of violent offending among individuals with schizophrenia and should be considered in violence risk assessment.

Trajectories leading to autism spectrum disorders are affected by paternal age: findings from two nationally representative twin studies

BACKGROUND

Despite extensive efforts, the causes of autism remain unknown. Advancing paternal age has been associated with various neurodevelopmental disorders. We aim to investigate three unresolved questions: (a) What is the association between paternal age and autism spectrum disorders (ASD)?; (b) Does paternal age moderate the genetic and environmental etiological factors for ASD? (c) Does paternal age affect normal variation in autistic-like traits?

METHODS

Two nationally representative twin studies from Sweden (n = 11, 122, assessed at age 9 or 12) and the UK (n = 13, 524, assessed at age 9) were used. Categorical and continuous measures of ASD, autistic-like traits and autistic similarity were calculated and compared over paternal age categories.

RESULTS

Both cohorts showed a strong association between paternal age and the risk for ASD. A U-shaped risk association could be discerned since the offspring of both the youngest and oldest fathers showed an elevation in the risk for ASD. Autistic similarity increased with advancing paternal age in both monozygotic and dizygotic twins. Both cohorts showed significantly higher autistic-like traits in the offspring of the youngest and oldest fathers.

CONCLUSIONS

Phenomena associated with paternal age are clearly involved in the trajectories leading to autistic-like traits and ASD. Mechanisms influencing the trajectories might differ between older and younger fathers. Molecular genetic studies are now needed in order to further understand the association between paternal age and ASD, as well as normal variation in social, language, and repetitive behaviors in the general population.

The Autism--Tics, AD/HD and other Comorbidities (A-TAC) telephone interview: convergence with the Child Behavior Checklist (CBCL)

OBJECTIVE

To compare telephone interview screening for child psychiatric/neuropsychiatric disorders using the inventory of Autism-Tics, Attention deficit/hyperactivity disorder (AD/HD) and other Comorbidities (A-TAC) with results from the Child Behavior Checklist (CBCL).

BACKGROUND

The A-TAC is a parent telephone interview focusing on autism spectrum disorders (ASDs) and co-existing problems, developed for lay interviewers.

SUBJECTS AND METHODS

A-TAC telephone interviews and CBCL questionnaires were obtained from parents of 106 Swedish twin pairs aged 9 and 12 years.

RESULTS

Correlations between A-TAC modules and CBCL scales aimed at measuring similar concepts were generally significant albeit modest, with correlation coefficients ranging from 0.30 through 0.55.

CONCLUSION

The A-TAC has convergent validity with the CBCL in several problem areas, but the A-TAC also provides more detailed and specific assessments of ASD symptoms and related neuropsychiatric problems.

Non-medical aspects of civilian-military collaboration in management of major incidents

Purpose

Disasters and major incidents demand a multidisciplinary management. Recent experiences from terrorist attacks worldwide have resulted in a search for better assessment of the needs, resources, and knowledge in the medical and non-medical management of these incidents and also actualized the need for collaboration between civilian and military healthcare. The aim of this study was to evaluate the impact of the civilian–military collaboration in a Swedish context with the main focus on its non-medical management.

Method

An exercise, simulating a foreign military attack centrally on Swedish soil, was designed, initiated, and conducted by a team consisting of civilian and military staff. Data were collected prospectively and evaluated by an expert team.

Results

Specific practical and technical issues were presented in collaboration between civilian and military staffs. In addition, shortcomings in decision-making, follow-up, communication, and collaboration due to prominent lack of training and exercising the tasks and positions in all managerial levels of the hospital were identified.

Conclusion

Current social and political unrests and terror attacks worldwide necessitate civilian–military collaboration. Such collaboration, however, needs to be synchronized and adjusted to avoid preventable medical and non-medical consequences. Simulation exercises might be one important source to improve such collaboration.

Incidence and characteristics of severe exercise-associated collapse at the world's largest half-marathon

Background

Whilst many health benefits are associated with regular exercise, medical complications may occur during higher-intensity activities, such as long distance running contests. The most common complication is collapse. However, the incidence and characteristics of these collapses are not very well studied.

Method

This is a retrospective study of severe collapse, defined as a patient in need of advanced medical care after a collapse, during the large Gothenburg’s half marathon, Göteborgsvarvet. The study included 230,501 competitors during the study-period of 5 years (2013–2017) with data being collected from medical race tents and using ambulance data. Vital signs, treatment and blood gas samples were noted and analyzed.

Results

The incidence of severe collapse was 1.53 per 1000 starting runners. The average age for patients was 34 years old and no difference in incidence were seen between male and female runners. The typical collapsed runner presented with tachycardia, normal systolic blood pressure, elevated body temperature and metabolic acidosis. The most common medical encounter was exercise-associated collapse.

Conclusion

The incidence of severe collapse was similar to findings in other studies, even though this study was set in different part of the world. Typical characteristics of a collapsed runner were identified providing new information which could be beneficial in the medical planning of larger running competitions and future preventative interventions. Importantly, life threatening conditions seem uncommon; no case of hyponatremia and only two cases of hypoglycemia were seen.

The Swedish Version of the Parent-Rated Junior Temperament and Character Inventory (J–TCI)

To evaluate the psychometric characteristics of the Swedish version of the Junior Temperament and Character Inventory (J–TCI), it was sent to parents of 9- and 12-yr.-old twins in Sweden. The final number of responders was 196 parents who rated 92 female and 104 male twin pairs. The inventory of one twin, randomly chosen from each pair, was included in the analyses. Reward Dependence, Persistence, and Cooperativeness were scored higher in girls; Novelty Seeking was higher in the 9-yr.-olds and Persistence in the 12-yr.-olds. Pearson's correlations showed that some dimensions were not statistically independent from each other, even if the covariance was moderate. Internal consistency (Cronbach's alpha) was satisfactory for Harm Avoidance, Novelty Seeking, Self-Directedness, and Cooperativeness (.68–.81), while it was lower in those dimensions that had fewer items. The Swedish parent version of the J–TCI shared about the same psychometric characteristics as found in international samples.

The Second Opinion Dispatch- Evaluating Decisions Made by an Ambulance Dispatch Center

BACKGROUND: The efficacy and precision of dispatching right ambulance to right patient demands a proper decision-making. Wrong decisions may lead to overloading of emergency departments and shortage of ambulances. The aim of this study was to evaluate and improve the process of prehospital resource allocation conducted by a Swedish ambulance dispatch center.METHODS: A team of three experienced ambulance and dispatch nurses evaluated the decisions made by the dispatch center. The method chosen was “Action Research” divided into five actions during 76 days. In the first action, the team listened passively to the calls. The team gradually increased its involvement in the process of decision-making during the actions.RESULTS: During the actions, specific keywords indicating a need for evaluation were identified. The results showed a need to change the primary decisions in 486 cases out of 24,800 calls (2%). The most common measure after an evaluation was to change an ordinary ambulance transportation to an assessment vehicle staffed by a nurse or a physician who would select an appropriate care level (hospital vs. primary healthcare).CONCLUSION: This model not only optimized the prehospital resources but also changed the process of decision-making at the dispatch center and improved their staffs’ ability to optimize the allocation of emergency resources.

Characteristics and motivational factors for joining a lay responder system dispatch to out-of-hospital cardiac arrests

BACKGROUND

There has been in increase in the use of systems for organizing lay responders for suspected out-of-hospital cardiac arrests (OHCAs) dispatch using smartphone-based technology. The purpose is to increase survival rates; however, such systems are dependent on people's commitment to becoming a lay responder. Knowledge about the characteristics of such volunteers and their motivational factors is lacking. Therefore, we explored characteristics and quantified the underlying motivational factors for joining a smartphone-based cardiopulmonary resuscitation (CPR) lay responder system.

METHODS

In this descriptive cross-sectional study, 800 consecutively recruited lay responders in a smartphone-based mobile positioning first-responder system (SMS-lifesavers) were surveyed. Data on characteristics and motivational factors were collected, the latter through a modified version of the validated survey "Volunteer Motivation Inventory" (VMI). The statements in the VMI, ranked on a Likert scale (1-5), corresponded to(a) intrinsic (an inner belief of doing good for others) or (b) extrinsic (earning some kind of reward from the act) motivational factors.

RESULTS

A total of 461 participants were included in the final analysis. Among respondents, 59% were women, 48% between 25 and 39 years of age, 37% worked within health care, and 66% had undergone post-secondary school. The most common way (44%) to learn about the lay responder system was from a CPR instructor. A majority (77%) had undergone CPR training at their workplace. In terms of motivation, where higher scores reflect greater importance to the participant, intrinsic factors scored highest, represented by the category values (mean 3.97) followed by extrinsic categories reciprocity (mean 3.88) and self-esteem (mean 3.22).

CONCLUSION

This study indicates that motivation to join a first responder system mainly depends on intrinsic factors, i.e. an inner belief of doing good, but there are also extrinsic factors, such as earning some kind of reward from the act, to consider. Focusing information campaigns on intrinsic factors may be the most important factor for successful recruitment. When implementing a smartphone-based lay responder system, CPR instructors, as a main information source to potential lay responders, as well as the workplace, are crucial for successful recruitment.