Conducting genetic epidemiology studies of autism spectrum disorders: issues in matching

Perinatal Depression and Risk of Suicidal Behavior

Importance

Suicidal ideation is common among women with perinatal depression (PND). However, prospective data are limited on the risk, particularly long-term risk, of suicidal behavior (suicide attempt and completed suicide) among women with perinatal depression.

Objective

To examine the association between PND and risk of short- and long-term suicidal behavior.

Design, Setting, and Participants

A nationwide population-matched cohort study was conducted in Sweden including 86 551 women with PND from 2001 to 2017 and 865 510 unaffected women individually matched on age and calendar year at delivery. Sibling comparison was used to account for familial confounding. Data were analyzed from January 2022 to November 2023.

Exposure

PND was identified through depression diagnosis or filled prescriptions of antidepressants from pregnancy to 1 year post partum in registers.

Main Outcomes and Measures

All women were followed up for the first event of suicidal behavior recorded in registers. Hazard ratios (HR) of suicidal behavior were estimated using time-to-event analysis.

Results

Women with PND (86 551 participants) received a diagnosis at a mean (SD) age of 30.67 (5.23) years. During a median (IQR) follow-up of 6.91 (3.62-10.88) years, 3604 events of suicidal behavior (incidence rate [IR], 5.62 per 1000 person-years) were identified among women with PND and 6445 (IR, 1.01 per 1000 person-years) among population-unaffected women. Women with PND had an elevated risk of suicidal behavior when compared with matched unaffected women (HR, 3.15; 95% CI, 2.97-3.35). Comparable, albeit somewhat attenuated, associations were yielded when comparing PND women with their PND-free sisters (HR, 2.75; 95% CI, 2.10-3.61). In the population-matched cohort, the association was greater for postnatal depression and among women without a history of psychiatric disorders. The excess risk was pronounced during the first year after diagnosis (HR, 7.20; 95% CI, 6.07-8.54), yet remained statistically significant during 5 to 18 years of follow-up (HR, 2.34; 95% CI, 2.12-2.57).

Conclusions and Relevance

In this nationwide cohort study, women with PND were at an increased risk of suicidal behavior, particularly within the first year after diagnosis with persistent risk elevations throughout the 18 years of follow-up, highlighting the need for vigilant clinical monitoring of this vulnerable group.

A functional polymorphism of the brain derived neurotrophic factor gene and cortical anatomy in autism spectrum disorder

Autism Spectrum Disorder (ASD) is associated with both (i) post-mortem and neuroimaging evidence of abnormal cortical development, and (ii) altered signalling in Brain Derived Neurotrophic Factor (BDNF) pathways - which regulate neuroproliferative and neuroplastic processes. In healthy controls genotype at a single nucleotide polymorphism that alters BDNF signalling (Val66met) has been related to regional cortical volume. It is not known however if this influence on brain development is intact in ASD. Therefore we compared the relationship between genotype and cortical anatomy (as measured using in vivo Magnetic Resonance Imaging) in 41 people with ASD and 30 healthy controls. We measured cortical volume, and its two sole determinants - cortical thickness and surface area - which reflect differing neurodevelopmental processes. We found “Group-by-Genotype” interactions for cortical volume in medial (caudal anterior cingulate, posterior cingulate) and lateral (rostral middle, lateral orbitofrontal, pars orbitalis and pars triangularis) frontal cortices. Furthermore, within (only) these regions “Group-by-Genotype” interactions were also found for surface area. No effects were found for cortical thickness in any region. Our preliminary findings suggest that people with ASD have differences from controls in the relationship between BDNF val66met genotype and regional (especially frontal) cortical volume and surface area, but not cortical thickness. Therefore alterations in the relationship between BDNF val66met genotype and surface area in ASD may drive the findings for volume. If correct, this suggests ASD is associated with a distorted relationship between BDNF val66met genotype and the determinants of regional cortical surface area – gyrification and/or sulcal positioning.

Studying the emergence of autism spectrum disorders in high-risk infants: methodological and practical issues

Detecting early signs of autism is essential for timely diagnosis and initiation of effective interventions. Several research groups have initiated prospective studies of high-risk populations including infant siblings, to systematically collect data on early signs within a longitudinal design. Despite the potential advantages of prospective studies of young children at high-risk for autism, there are also significant methodological, ethical and practical challenges. This paper outlines several of these challenges, including those related to sampling (e.g., defining appropriate comparison groups), measurement and clinical implications (e.g., addressing the needs of infants suspected of having early signs). We suggest possible design and implementation strategies to address these various challenges, based on current research efforts in the field and previous studies involving high-risk populations.

Language development among the siblings of children with autistic spectrum disorder

Language development in 32 preschool siblings (aged 2-6 years) of children with diagnosed autistic spectrum disorder (ASD) was compared with that of a control group of 28 typical preschool children. Groups were matched by siblings' age, gender, maternal educational level and family income. The mean ages of the siblings group and the control group were 4.2 and 4.4 years. Eight of the siblings had delayed language development, of whom three received a diagnosis of developmental language disorder (DLD) and one of ASD. The sibling with ASD and two of those with DLD were excluded; the remaining 29 siblings and the controls were administered the Stanford-Binet IV. Verbal IQs of siblings were not significantly different from the control group. Siblings of children with ASD associated with intellectual impairment ('mental retardation' (MR) in Thailand) had significantly lower verbal IQ scores than siblings of children with ASD but without MR.

Stereotyped motor behaviors associated with autism in high-risk infants: a pilot videotape analysis of a sibling sample

This study examined motor behaviors in a longitudinal cohort of infant siblings of children with autism. Stereotypic movements and postures occurring during standardized observational assessments at 12 and 18 months were coded from videotapes. Participants included eight infant siblings later diagnosed with autism spectrum disorder (ASD), a random sample of nine non-diagnosed siblings, and 15 controls. Videos were coded blind to diagnostic group. At 12 and 18 months the ASD group "arm waved" more frequently and at 18 months, one posture ("hands to ears") was more frequently observed in the ASD and non-diagnosed group compared to the controls. Overall, the siblings subsequently diagnosed with ASD and the comparison groups had considerable overlap in their repertoires of stereotyped behaviors.

Autism and 15q11-q13 disorders: Behavioral, genetic, and pathophysiological issues

New insights into biological factors that underlie autism may be gained by comparing autism to other neurodevelopmental disorders that have autistic features and relatively well-delineated genetic etiologies or neurobiological findings. This review moves beyond global diagnoses of autism and instead uses an endophenotypic approach to compare specific clusters of autistic symptomatology to features of chromosome 15q11-q13 disorders. Paternally or maternally derived deficiencies of 15q11-q13 result in Prader-Willi or Angelman syndromes, and we first use a global approach to review potential autism susceptibility genes in the 15q11-q13 region. We then use a more trait-based approach to suggest possible ties between specific phenotypic characteristics of autism and Prader-Willi syndrome, namely savant-like skills. We conclude with insights from pathophysiological studies that implicate altered development of specific neuron types and circuits in the cerebral cortex as part of the pathophysiological processes associated with autism and mental retardation.

Behavioral manifestations of autism in the first year of life

In the interest of more systematically documenting the early signs of autism, and of testing specific hypotheses regarding their underlying neurodevelopmental substrates, we have initiated a longitudinal study of high-risk infants, all of whom have an older sibling diagnosed with an autistic spectrum disorder. Our sample currently includes 150 infant siblings, including 65 who have been followed to age 24 months, who are the focus of this paper. We have also followed a comparison group of low-risk infants. Our measures include a novel observational scale (the first, to our knowledge, that is designed to assess autism-specific behavior in infants), a computerized visual orienting task, and standardized measures of temperament, cognitive and language development. Our preliminary results indicate that by 12 months of age, siblings who are later diagnosed with autism may be distinguished from other siblings and low-risk controls on the basis of: (1) several specific behavioral markers, including atypicalities in eye contact, visual tracking, disengagement of visual attention, orienting to name, imitation, social smiling, reactivity, social interest and affect, and sensory-oriented behaviors; (2) prolonged latency to disengage visual attention; (3) a characteristic pattern of early temperament, with marked passivity and decreased activity level at 6 months, followed by extreme distress reactions, a tendency to fixate on particular objects in the environment, and decreased expression of positive affect by 12 months; and (4) delayed expressive and receptive language. We discuss these findings in the context of various neural networks thought to underlie neurodevelopmental abnormalities in autism, including poor visual orienting. Over time, as we are able to prospectively study larger numbers and to examine interrelationships among both early-developing behaviors and biological indices of interest, we hope this work will advance current understanding of the neurodevelopmental origins of autism.