Subthreshold and threshold attention deficit hyperactivity disorder symptoms in childhood: psychosocial outcomes in adolescence in boys and girls

OBJECTIVE

To examine the association between different levels of childhood attention deficit hyperactivity disorder (ADHD) symptoms and sex differences in psychosocial outcomes during adolescence.

METHOD

Swedish children (n = 4635) were screened for neuropsychiatric symptoms at age 9 or 12. ADHD symptoms were divided into three levels: screen-negative, screen-intermediate, and screen-positive. At follow-up (age 15), parents and teenagers filled out questionnaires regarding (i) hyperactivity/inattention, (ii) peer problems, (iii) school problems, (iv) internalizing problems, (v) antisocial behaviour, (vi) alcohol misuse, and (vii) drug misuse. All outcomes were controlled for symptoms of diagnostic categories other than ADHD.

RESULTS

Increasing levels of ADHD symptoms in childhood were associated with higher proportions of adolescents who displayed negative psychosocial outcomes. More girls than boys reported internalizing problems (all levels) and risky drug use (screen-intermediate and screen-positive only). More boys reported antisocial behaviour at the screen-negative and screen-intermediate levels, but at the screen-positive level, similar proportions of girls and boys displayed antisocial behaviour.

CONCLUSION

The findings support the view that ADHD symptoms, as well as their negative outcomes, are dimensionally distributed in the population and that adolescent girls and boys display different risk profiles. The findings confirm that ADHD symptoms are associated with higher risk of drug misuse in girls.

Impact of asthma medication and familial factors on the association between childhood asthma and attention-deficit/hyperactivity disorder: a combined twin- and register-based study: Epidemiology of Allergic Disease

BACKGROUND

Asthma and attention-deficit/hyperactivity disorder (ADHD) are prevalent in childhood and may cause functional impairment and stress in families. Previous research supports an association between asthma and ADHD in children, but several aspects of this relationship are unclear.

OBJECTIVE

Our aim was to study whether the association between asthma and ADHD is restricted to either the inattentive or the hyperactive/impulsive symptoms of ADHD, to explore the impact of asthma severity and asthma medication and the contribution of shared genetic and environmental risk factors on the asthma-ADHD relationship.

METHODS

Data on asthma, ADHD, zygosity and possible confounders were collected from parental questionnaires at 9 or 12 years on 20 072 twins through the Swedish Twin Register, linked to the Swedish Medical Birth Register, the National Patient Register and the Prescribed Drug Register. The association between asthma and ADHD, the impact of asthma severity and medication, was assessed by generalized estimating equations. Cross-twin-cross-trait correlations (CTCT) were estimated to explore the relative importance of genes and environment for the association.

RESULTS

Asthmatic children had a higher risk of also having ADHD [odds ratio (OR) 1.53, 95% confidence interval (CI): 1.16-2.02]. The association was not restricted to either of the two dimensions of ADHD. The magnitude of the association increased with asthma severity (OR 2.84, 95% CI: 1.86-4.35) for ≥ 4 asthma attacks in the last 12 months and was not affected by asthma treatment. The CTCTs possibly indicate that the genetic component in overlap of the disorders is weak.

CONCLUSIONS AND CLINICAL RELEVANCE

Childhood asthma, especially severe asthma, is associated with ADHD. Asthma medication seems not to increase the risk of ADHD. Clinicians should be aware of the potential of ADHD in asthma. Optimal asthma care needs to be integrated with effective evaluation and treatment of ADHD in children with co-existing disorders.

Language and mathematical problems as precursors of psychotic-like experiences and juvenile mania symptoms

BACKGROUND

Psychotic-like experiences (PLEs) and juvenile mania in adolescence index risk for severe psychopathology in adulthood. The importance of childhood problems with communication, reading, speech and mathematics for the development of PLEs and juvenile mania is not well understood.

METHOD

Through the Child and Adolescent Twin Study in Sweden, we identified 5812 children. The parents were interviewed about their children's development at age 9 or 12 years. At age 15 or 18 years, children and parents completed questionnaires targeting current PLEs and juvenile mania symptoms. Logistic regressions were used to assess associations between problems with communication, reading, speech and mathematics and PLEs/juvenile mania symptoms. To evaluate the relative importance of genes and environment in these associations, we used bivariate twin analyses based on structural equation models.

RESULTS

Children with parent-endorsed childhood problems with communication, reading and mathematics had an increased risk of developing auditory hallucinations and parental-reported juvenile mania symptoms in adolescence. The most consistent finding was that children with childhood problems with communication, reading and mathematics had an increased risk of developing auditory hallucinations [for example, the risk for self-reported auditory hallucinations at age 15 was increased by 96% for children with communication problems: OR (odds ratio) 1.96, 95% confidence interval (CI) 1.33-2.88]. The twin analyses showed that genetic effects accounted for the increased risk of PLEs and juvenile mania symptoms among children with communication problems.

CONCLUSIONS

Childhood problems with communication, reading and mathematics predict PLEs and juvenile mania symptoms in adolescence. Similar to the case for schizophrenia and bipolar disorder, PLEs and juvenile mania may share genetic aetiological factors.

A study of the possible association between adenosine A2A receptor gene polymorphisms and attention-deficit hyperactivity disorder traits

The adenosine A2A receptor (ADORA2A) is linked to the dopamine neurotransmitter system and is also implicated in the regulation of alertness, suggesting a potential association with attention-deficit hyperactivity disorder (ADHD) traits. Furthermore, animal studies suggest that the ADORA2A may influence ADHD-like behavior. For that reason, the ADORA2A gene emerges as a promising candidate for studying the etiology of ADHD traits. The aim of this study was to examine the relationship between ADORA2A gene polymorphisms and ADHD traits in a large population-based sample. This study was based on the Child and Adolescent Twin Study in Sweden (CATSS), and included 1747 twins. Attention-deficit hyperactivity disorder traits were assessed through parental reports, and samples of DNA were collected. Associations between six single nucleotide polymorphisms (SNPs) and ADHD traits were examined, and results suggested a nominal association between ADHD traits and three of these SNPs: rs3761422, rs5751876 and rs35320474. For one of the SNPs, rs35320474, results remained significant after correction for multiple comparisons. These results indicate the possibility that the ADORA2A gene may be involved in ADHD traits. However, more studies replicating the present results are warranted before this association can be confirmed.

The sociocommunicative deficit subgroup in anorexia nervosa: autism spectrum disorders and neurocognition in a community-based, longitudinal study

BACKGROUND

A subgroup of persons with anorexia nervosa (AN) have been proposed to have sociocommunicative problems corresponding to autism spectrum disorders [ASDs, i.e. DSM-IV pervasive developmental disorders (PDDs): autistic disorder, Asperger's disorder, PDD not otherwise specified (NOS)]. Here, clinical problems, personality traits, cognitive test results and outcome are compared across 16 subjects (32%) with teenage-onset AN who meet or have met ASD criteria (AN+ASD), 34 ASD-negative AN subjects and matched controls from a longitudinal Swedish study including four waves of independent assessments from the teens to the early thirties.

METHOD

The fourth wave included the Structured Clinical Interview for DSM-IV (SCID)-I and the SCID-II (cluster C, i.e. 'anxious' PDs) interviews, the Asperger Syndrome Diagnostic Interview, self-assessments by the Autism Spectrum Quotient and the Temperament and Character Inventory, neurocognitive tests by subscales from the Wechsler scales, continuous performance tests, Tower of London, and Happé's cartoons.

RESULTS

The ASD assessments had substantial inter-rater reliability over time (Cohen's κ between 0.70 and 0.80 with previous assessments), even if only six subjects had been assigned a diagnosis of an ASD in all four waves of the study, including retrospective assessments of pre-AN neurodevelopmental problems. The AN+ASD group had the highest prevalence of personality disorders and the lowest Morgan-Russell scores. The non-ASD AN group also differed significantly from controls on personality traits related to poor interpersonal functioning and on neurocognitive tests.

CONCLUSIONS

A subgroup of subjects with AN meet criteria for ASDs. They may represent the extreme of neurocognitive and personality problems to be found more generally in AN.

Lower birth weight indicates higher risk of autistic traits in discordant twin pairs

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder of complex etiology. Although strong evidence supports the causal role of genetic factors, environmental risk factors have also been implicated. This study used a co-twin-control design to investigate low birth weight as a risk factor for ASD.

METHOD

We studied a population-based sample of 3715 same-sex twin pairs participating in the Child and Adolescent Twin Study of Sweden (CATSS). ASD was assessed using a structured parent interview for screening of ASD and related developmental disorders, based on DSM-IV criteria. Birth weight was obtained from medical birth records maintained by the Swedish Medical Birth Registry.

RESULTS

Twins lower in birth weight in ASD-discordant twin pairs (n=34) were more than three times more likely to meet criteria for ASD than heavier twins [odds ratio (OR) 3.25]. Analyses of birth weight as a continuous risk factor showed a 13% reduction in risk of ASD for every 100 g increase in birth weight (n=78). Analysis of the effect of birth weight on ASD symptoms in the entire population (most of whom did not have ASD) showed a modest association. That is, for every 100 g increase in birth weight, a 2% decrease in severity of ASD indexed by scores on the Autism - Tics, attention-deficit hyperactivity disorder (AD/HD), and other Comorbidities (A-TAC) inventory would be expected in the sample as a whole.

CONCLUSIONS

The data were consistent with the hypothesis that low birth weight confers risk to ASD. Thus, although genetic effects are of major importance, a non-genetic influence associated with birth weight may contribute to the development of ASD.

Autistic-like traits and their association with mental health problems in two nationwide twin cohorts of children and adults

BACKGROUND

Autistic-like traits (ALTs), that is restrictions in intuitive social interaction, communication and flexibility of interests and behaviors, were studied in two population-based Swedish twin studies, one in children and one in adults: (1) to examine whether the variability in ALTs is a meaningful risk factor for concomitant attention deficit hyperactivity disorder (ADHD), anxiety, conduct problems, depression and substance abuse, and (2) to assess whether common genetic and environmental susceptibilities can help to explain co-existence of ALTs and traits associated with such concomitant problems.

METHOD

Two nationwide twin cohorts from Sweden (consisting of 11 222 children and 18 349 adults) were assessed by DSM-based symptom algorithms for autism. The twins were divided into six groups based on their degree of ALTs and the risk for concomitant mental health problems was calculated for each group. Genetic and environmental susceptibilities common to ALTs and the other problem types were examined using bivariate twin modeling.

RESULTS

In both cohorts, even the lowest degree of ALTs increased the risk for all other types of mental health problems, and these risk estimates increased monotonically with the number of ALTs. For all conditions, common genetic and environmental factors could be discerned. Overall, the phenotypic correlation between ALTs and the traits examined were less pronounced in adulthood than in childhood and less affected by genetic compared with environmental factors.

CONCLUSIONS

Even low-grade ALTs are relevant to clinical psychiatry as they increase the risk for several heterotypical mental health problems. The association is influenced partly by common genetic and environmental susceptibilities. Attention to co-existing ALTs is warranted in research on a wide range of mental disorders.

A twin study of autism symptoms in Sweden

This study aimed to identify empirically the number of factors underlying autism symptoms-social impairments, communication impairments, and restricted repetitive behaviors and interests-when assessed in a general population sample. It also investigated to what extent these autism symptoms are caused by the same or different genetic and environmental influences. Autistic symptoms were assessed in a population-based twin cohort of >12,000 (9- and 12-year-old) children by parental interviews. Confirmatory factor analyses, principal component analyses and multivariate structural equation model fitting were carried out. A multiple factor solution was suggested, with nearly all analyses pointing to a three-factor model for both boys and girls and at both ages. A common pathway twin model fit the data best, which showed that there were some underlying common genetic and environmental influences across the different autism dimensions, but also significant specific genetic effects on each symptom type. These results suggest that the autism triad consists of three partly independent dimensions when assessed in the general population, and that these different autism symptoms, to a considerable extent, have partly separate genetic influences. These findings may explain the large number of children who do not meet current criteria for autism but who show some autism symptoms. Molecular genetic research may benefit from taking a symptom-specific approach to finding genes associated with autism.

Reduced cerebrospinal fluid BACE1 activity in multiple sclerosis

Background

Cell and animal experiments have shown that β-site APP-cleaving enzyme 1 (BACE1) may be involved in myelination.

Objective

Here, we assess the association of cerebrospinal fluid (CSF) BACE1 activity with multiple sclerosis (MS).

Methods

BACE1 activity and levels of secreted amyloid precursor protein (APP) and amyloid-β (Aβ) isoforms were analyzed in CSF from 100 patients with MS and 114 neurologically healthy controls. Patients with systemic lupus erythematosus (SLE), 26 with and 41 without cerebral engagement, were also included to enable comparisons with regards to another autoimmune disease. A subset of patients with MS and controls underwent a second lumbar puncture after 10 years.

Results

MS patients had lower CSF BACE1 activity than controls ( P = 0.03) and patients with cerebral SLE ( P < 0.001). Patients with cerebral SLE had higher BACE1 activity than any other group ( P < 0.05 for all comparisons). BACE1 activity correlated with the different amyloid markers in all study groups. BACE1 activity decreased over 10 years in the MS group ( P = 0.039) and correlated weakly with clinical disease severity scores in an inverse manner.

Conclusions

These results suggest an involvement of BACE1 in the MS disease process.

Cerebrospinal fluid protein reactions during non-neurological surgery

OBJECTIVE

To study changes in cerebrospinal fluid (CSF) protein markers of blood-CSF barrier integrity and immunological reactions during surgical stress.

SUBJECTS AND METHODS

Thirty-five patients without neurological or psychiatric disorders undergoing knee replacements had CSF and serum samples drawn from spinal and arterial catheters before, 3 h after and the morning after surgery.

RESULTS

Serum albumin decreased during surgery and CSF albumin decreased during and after surgery, and, as a consequence, the CSF/serum albumin ratio decreased significantly during the study period, especially after the intervention. In contrast, CSF concentrations of beta-2-microglobuline (beta2M) increased significantly during surgery and remained high. The CSF general marker beta-trace protein (betaTP) remained unchanged.

CONCLUSIONS

Central nervous system protein reactions to a non-neurological surgical intervention include sharply decreased permeability of albumin into the CSF and signs of intrathecal inflammatory activity.

Increased CSF/serum albumin ratio: a recurrent finding in violent offenders

OBJECTIVE

To test the hypothesis that cerebrospinal fluid (CSF)/ serum albumin ratios are increased in violent offenders.

SUBJECTS AND METHODS

In a previous study of violent offenders, we found significantly higher CSF/serum album ratios (as a sign of increased blood-brain barrier permeability) in violent offenders than in healthy controls. For the present replication study, we recruited a new group of 28 violent offenders, aged 45 years or younger, and 20 new control subjects.

RESULTS

The albumin ratio was again significantly higher in the offender group (mean 6.2) than in the control group (mean 4.6) (P = 0.012). Substance abuse or current medication did not appear to explain this finding.

CONCLUSION

Increased CSF/serum albumin ratios are an unspecific sign of neurological dysfunction in subgroups of violent offenders.