Christine Till

York University · Department of Psychology

Behavioral traits of autism spectrum disorder (ASD) typically present in early childhood, underscoring the importance of screening tools for the early identification of ASD. The current study compared scores on the Social Responsiveness Scale-Second Edition (SRS-2) Preschool Form between the US standardization sample (n = 247) and a Canadian cohort...

Background Early life exposure to lead, mercury, polychlorinated biphenyls (PCBs), polybromide diphenyl ethers (PBDEs), organophosphate pesticides (OPPs), and phthalates have been associated with lowered IQ in children. In some studies, these neurotoxicants impact males and females differently. We aimed to examine the sex-specific effects of exposu...

Background Prenatal fluoride exposure can have adverse effects on children’s development; however, associations with visual and cardiac autonomic nervous system functioning are unknown. We examined associations between prenatal fluoride exposure and visual acuity and heart rate variability (HRV) in 6-month-old infants. Methods We used data from Ca...

Background Fluoride may be a developmental neurotoxicant at elevated exposures. We merged new data from a prospective Odense Child Cohort (OCC) with results from two previous birth cohort studies from Mexico and Canada to characterize the dose–effect relationship in greater detail. Methods The OCC contributed 837 mother–child pairs to the total of...

Background: Exposure to perfluoroalkyl substances (PFAS) has been shown to be neurotoxic in experimental studies, but epidemiological evidence linking prenatal PFAS exposure to child neurodevelopment is equivocal and scarce. Objective: To quantify associations between prenatal exposure to legacy PFAS and children's intelligence (IQ) and executiv...

Background: While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development. Objectives: We evaluated associations between fluoride exposure and hypothyroidism in a...

Background Lead exposure remains highly prevalent worldwide despite decades of research highlighting its link to numerous adverse health outcomes. In addition to well-documented effects on cognition, there is growing evidence of an association with antisocial behavior, including aggression, conduct problems, and crime. An updated systematic review...

In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys’ a...

Early-life exposures to toxic chemicals can adversely impact brain development. Understanding people's knowledge of the impact of toxic chemicals on brain development is critical to reduce widespread exposure to chemicals. Yet it is unknown what people know about risks of toxic chemicals and how to reduce exposures. We developed and validated the q...

Objective Prenatal exposure to fluoride has been associated with adverse neurodevelopmental outcomes. However, the neuropsychological profile of fluoride's developmental neurotoxicity at low levels and the stability of this relationship across childhood has not been characterized. We investigated the longitudinal and domain specific effect of prena...

Introduction : Myelin oligodendrocyte glycoprotein antibodies are identified in approximately 30-50% of youth with pediatric-onset acquired demyelinating syndromes. Little is known about the cognitive sequelae of relapsing myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) with onset in childhood or adolescence.Overall, adults...

Long-term cognitive deficits have been observed in some children who experience an acquired demyelinating syndrome (ADS). We examined changes in cognitive functioning over the first two years following incident ADS andtested whether normalized brain and thalamic volume accounted for decline over time. Twenty-five youth (mean age 12.8 years) with AD...

Objective : Fluoride exposure >1.5 mg/L from water has been associated with adverse pregnancy and birth outcomes. Little is known, however, about the effect of fluoride at levels consistent with water fluoridation (i.e., 0.7 mg/L) on pregnancy and birth outcomes. We examined the relationship between maternal fluoride exposure, fertility, and birth...

Foods and beverages provide a source of fluoride exposure in Mexico. While high fluoride concentrations are neurotoxic, recent research suggests that exposures within the optimal range may also pose a risk to the developing brain. This prospective study examined whether dietary fluoride intake during pregnancy is associated with toddlers' neurodeve...

Objective The limbic system is involved in memory and in processing of emotional stimuli. We measured volume of the hippocampus, amygdala, and thalamus, and assessed their relative contribution to episodic memory and emotion identification in POMS. Method Sixty-five POMS participants (Mage = 18.3 ± 3.9 years; 48 female (73.8%)), average disease du...

Drinking water is a major source of dietary fluoride intake in communities with water fluoridation. We examined the association between urinary fluoride adjusted for specific gravity (UFSG) and tap water fluoride levels, by age and sex, among individuals living in Canada. Participants included 1629 individuals aged 3 to 79 years from Cycle 3 (2012–...

As a guide to establishing a safe exposure level for fluoride exposure in pregnancy, we applied benchmark dose modeling to data from two prospective birth cohort studies. We included mother–child pairs from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort in Mexico and the Maternal-Infant Research on Environmental Chem...

Objective: We evaluated performance on the Penn Computerized Neurocognitive Battery (PCNB), a tool assessing accuracy and response time across four cognitive domains, alongside the Symbol Digit Modalities Test (SDMT), a measure of processing speed commonly used in MS. We determined whether performance decrements are more likely to be detected on m...

Background Fluoride has been associated with IQ deficits during early brain development, but the period in which children are most sensitive is unknown. Objective We assessed effects of fluoride on IQ scores across prenatal and postnatal exposure windows. Methods We used repeated-exposures from 596 mother-child pairs in the Maternal-Infant Resear...

Background Fluoride from dietary and environmental sources may concentrate in calcium-containing regions of the body such as the pineal gland. The pineal gland synthesizes melatonin, a hormone that regulates the sleep-wake cycle. We examined associations between fluoride exposure and sleep outcomes among older adolescents and adults in Canada. Met...

Fluoride, which may be toxic to the developing brain, is added to salt in Mexico and drinking water in Canada to prevent dental caries. We compared childhood urinary fluoride (CUF) concentrations in Mexico City and Canada to characterize patterns of fluoride exposure in these two populations. We also examined associations of CUF with dietary and wa...

As a safe exposure level for fluoride in pregnancy has not been established, we used data from two prospective studies for benchmark dose modeling. We included mother-child pairs from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort in Mexico and the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort in...

Purpose of review: A growing body of evidence suggests adverse neurodevelopmental effects of early-life exposure to fluoride that may differ depending on timing of exposure and sex of the exposed. We conducted a literature search to identify the animal and human epidemiologic studies that examined sex-specific neurodevelopmental differences in res...

Over the past 75 years, health authorities have declared that community water fluoridation—a practice that reaches over 400 million worldwide—is safe. Yet, studies conducted in North America examining the safety of fluoride exposure in pregnancy were nonexistent. When a Canadian study reported that higher fluoride exposure in pregnant women was ass...

PURPOSE To investigate longitudinal associations between physical activity (PA) and neurocognitive problems in adult survivors of childhood cancer. METHODS A total of 12,123 5-year survivors diagnosed between 1970 and 1999 (median [range] age at diagnosis, 7 [0-21] years, time since diagnosis at baseline, 16 [6-30] years) and 720 siblings self-rep...

In Reply We appreciate the widespread interest in our study and the opportunity to respond to the critiques and clarify some facts.

Background: Infant consumption of formula reconstituted with fluoridated water can lead to excessive fluoride intake. We examined the association between fluoride exposure in infancy and intellectual ability in children who lived in fluoridated or non-fluoridated cities in Canada. Methods: We examined 398 mother-child dyads in the Maternal-Infan...

Background: We assessed whether clinical characteristics and health-related quality of life (HRQOL) are independently associated with subsequent hospitalizations and physician visits among children with multiple sclerosis (MS); and whether differences in HRQOL account for differences in physician visits between children with MS, monophasic acquire...

Background: Exposure to fluoride has been linked with increased prevalence of attention deficit hyperactivity disorder (ADHD) in the United States and symptoms of inattention in Mexican children. We examined the association between fluoride exposure and attention outcomes among youth living in Canada. Method: We used cross-sectional data collect...

Importance The potential neurotoxicity associated with exposure to fluoride, which has generated controversy about community water fluoridation, remains unclear. Objective To examine the association between fluoride exposure during pregnancy and IQ scores in a prospective birth cohort. Design, Setting, and Participants This prospective, multicent...

Early caregiving is one of the strongest influences on children's development, and among the most significant modifiable environmental factor. The aim of this study was to explore the association between quality of caregiver-infant interactions and neurodevelopment of infants living in banana-growing communities in rural Costa Rica characterized as...

Objectives: Youth and young adults with pediatric-onset multiple sclerosis (MS) are vulnerable to executive dysfunction; however, some patients do not demonstrate functional deficits despite showing abnormalities on structural magnetic resonance imaging (MRI). Cognitively intact adults with MS have shown enhanced activation patterns relative to he...

Background: The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a computerized tool used to measure cognitive function in diverse populations and is sensitive for assessing developmental changes in children. Although CANTAB has been used in several countries, its applicability in a Mexican child population is unknown. This study exa...

Background: Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation. Objective: Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations...

BACKGROUND: Fluoride exposures have not been established for pregnant women who live in regions with and without community water fluoridation. OBJECTIVE: Our aim was to measure urinary fluoride levels during pregnancy. We also assessed the contribution of drinking-water and tea consumption habits to maternal urinary fluoride (MUF) concentrations an...

Background: Fluoride exposure has the potential to disrupt thyroid functioning, though adequate iodine intake may mitigate this effect. This is the first population-based study to examine the impact of chronic low-level fluoride exposure on thyroid function, while considering iodine status. The objective of this study was to determine whether urina...

Background: Epidemiologic and animal-based studies have raised concern over the potential impact of fluoride exposure on neurobehavioral development as manifested by lower IQ and deficits in attention. To date, no prospective epidemiologic studies have examined the effects of prenatal fluoride exposure on behavioral outcomes using fluoride biomarke...

Youth with multiple sclerosis (MS) often experience cognitive impairment and psychosocial disturbances. We describe the relationship between memory function, psychosocial skills, and brain volume in 32 patients with pediatric-onset MS and 30 controls. Amygdala volume was significantly lower in patients compared with controls. In general, poorer mem...

Objective: To determine the frequency of cortical lesions (CLs) in patients with pediatric-onset multiple sclerosis (POMS) using multi-contrast magnetic resonance imaging (MRI), and the relationship between frontal CL load and upper limb dexterity assessed with the Nine-Hole Peg Test (9-HPT). Methods: Participants completed the 9-HPT and were im...

Background/aim Recent studies report an inverse association between fluoride (F) exposure and IQ in children, but few included individual measures of exposure or assessed associations with prenatal exposure using a prospective study design. Methods This study utilised the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth co...

Objective: To investigate the feasibility and experiences of paediatric-onset multiple sclerosis (MS) patients completing a working memory training programme. Methods: Nine paediatric-onset MS patients (mean age 19.3 ± 4.1 years) identified as having attention and/or working memory difficulties underwent a five-week (five days/week) internet-based...

Processing speed is a frequently affected cognitive domain in pediatric multiple sclerosis (MS) and is commonly assessed using the Symbol Digit Modalities Test (SDMT). The objective of this study was to determine maturational trajectories in SDMT performance and baseline factors affecting trajectories in a sample of 82 pediatric MS individuals. Per...

Objectives Huntington disease (HD) is associated with a variety of cognitive deficits, with prominent difficulties in working memory (WM). WM deficits are notably compromised in early-onset and prodromal HD patients. This study aimed to determine the feasibility of a computerized WM training program (Cogmed QM), novel to the HD population. Methods...

TREND checklist. (PDF)

Post-training interview questions. (DOCX)

Trial study protocol. (PDF)

Decreased information processing speed (IPS) is frequently reported in pediatric multiple sclerosis (MS) patients. The computerized version of the Symbol Digit Modalities Test (c-SDMT) measures IPS over eight consecutive trials per session and additionally captures changes in performance within the session. Here, we establish normative c-SDMT perfo...

Objectives: The aim of this study was to describe cognitive, academic, and psychosocial outcomes after an incident demyelinating event (acquired demyelinating syndromes, ADS) in childhood and to investigate the contribution of brain lesions and confirmed MS diagnosis on outcome. Methods: Thirty-six patients with ADS (mean age=12.2 years, SD=2.7,...

Objectives: To investigate physical activity levels in youth with multiple sclerosis and monophasic acquired demyelinating syndromes ([mono-ADS], ie, children without relapsing disease) compared with healthy controls and to determine factors that contribute to engagement in physical activity. We hypothesized that greater physical activity goal set...

Background Huntington’s disease (HD) is associated with a variety of cognitive deficits, with prominent deficits in working memory (WM). These deficits can occur in the early stage of the disease and undermine quality of life. Currently, there are no established treatments for these symptoms. Aims The feasibility of implementing a home-based, comp...

In comparison with the large body of evidence on cognitive functioning in adults with multiple sclerosis (MS), there is limited information on cognition in pediatric-onset MS (POMS). Unique vulnerabilities in POMS can derive from having a disease that occurs during key periods of ageexpected brain growth, active myelination in the CNS, and maturati...

Background: Reduced white matter (WM) integrity is a fundamental aspect of pediatric multiple sclerosis (MS), though relations to resting-state functional MRI (fMRI) connectivity remain unknown. The objective of this study was to relate diffusion-tensor imaging (DTI) measures of WM microstructural integrity to resting-state network (RSN) functiona...

Differences Between Groups in White Matter AD and RD. WM skeleton (green) depicting areas in which the pediatric-onset MS group demonstrated higher (blue) (Figure a) AD and (Figure b) RD compared to the healthy control group (p < .01 corrected). MNI152 template slice coordinates are also reported. (TIF)

Objective: This study aimed to determine the extent and pattern of brain activation elicited by a functional magnetic resonance imaging version of the Symbol Digit Modalities Test (fMRI-SDMT), a task of information processing speed, in pediatric-onset multiple sclerosis (MS) patients as compared to sex- and age-matched non-MS self-reported healthy...

A few studies have examined the prevalence of cortical lesions (CLs) in pediatric-onset MS (poMS) using double inversion recovery (DIR) at 1.5T and 3T. In this study we used a multimodal MRI reading protocol to determine the frequency of lesions that affect the cortex in 24 poMS patients. CLs occurred in our group in 79% of the cases.

Objective: To evaluate resting-state functional connectivity (FC) and relationship to brain volumes and cognition in a sample of cognitively preserved pediatric-onset multiple sclerosis (MS) patients. Methods: Sixteen cognitively intact pediatric-onset MS patients and 15 healthy age- and sex-matched controls underwent cognitive testing and 3T an...

Posterior fossa lesions are common in pediatric-onset multiple sclerosis (MS), which is of concern, given the known role of the cerebellum in cognition. To investigate the relationship between cerebellar pathology and cognitive function in youth with pediatric-onset MS. Twenty-eight pediatric-onset relapsing-remitting MS patients (21 girls; mean ag...

Background: Epidemiological and animal-based studies have suggested that prenatal and postnatal fluoride exposure has adverse effects on neurodevelopment. The aim of this study was to examine the relationship between exposure to fluoridated water and Attention-Deficit Hyperactivity Disorder (ADHD) prevalence among children and adolescents in the U...

Objective: To determine the impact of pediatric-onset multiple sclerosis (MS) on age-expected brain growth. Methods: Whole brain and regional volumes of 36 patients with relapsing-remitting MS onset prior to 18 years of age were segmented in 185 longitudinal MRI scans (2-11 scans per participant, 3-month to 2-year scan intervals). MRI scans of 2...

Background: Information processing speed (IPS) increases with myelination. Decreased IPS is often the first sign of neurocognitive impairment in children and teens with multiple sclerosis (MS). Prompt identification of pediatric MS patients with IPS impairment requires a sensitive testing metric that can be administered in a clinical setting. The c...

Cognitive impairment is often reported in pediatric-onset multiple sclerosis (MS). Using serial cognitive data from 35 individuals with pediatric-onset MS, this study examined how age at disease-onset and proxies of cognitive reserve may impact cognitive maturation over the course of childhood and adolescence. Neuropsychological evaluations were co...

Background: Early caregiving is one of the strongest influences on children's development, yet it has not been studied in the context of prenatal neurotoxin exposure. Epigenetic studies show that maternal nurturing promotes positive development in young rats who experienced prenatal environmental adversity. We explore the quality of caregiver-infan...

Impairments in visuospatial abilities are commonly reported in children and adolescents with multiple sclerosis (MS). Corpus callosum (CC) pathology occurs in patients with MS and may contribute to impairment in visuospatial perception, particularly when interhemispheric information transfer is required. This study used a global-local hierarchical...