Accumulating evidence suggests that corpus callosum development is critically involved in the emergence of behavioral and cognitive skills during the first two years of life and that structural abnormalities of the corpus callosum are associated with a variety of neurodevelopmental disorders. Indeed by adulthood ∼30% of individuals with agenesis of the corpus callosum (ACC), a congenital condition resulting in a partial or fully absent corpus callosum, exhibit phenotypic features consistent with autism spectrum disorder (ASD). However, very little is known about developmental similarities and/or differences among infants with ACC and infants who develop ASD. This study describes temperament in infants with ACC during the first year of life in comparison with a neurotypical control group. Additionally, it examines the potential contribution of disrupted callosal connectivity to early expression of temperament in ASD through comparison to children with high familial likelihood of ASD.

Longitudinal ratings of positive and negative emotionality were acquired at 6 and 12 months on the Infant Behavior Questionnaire-Revised across four groups of infants: isolated complete and partial ACC (n=104), high familial likelihood of ASD who do and do not have a confirmed ASD diagnosis (HL+ n=81, HL- n=282), and low-likelihood controls (LL- n=152).

Overall, the ACC group demonstrated blunted affect, with significantly lower positive and negative emotionality than LL controls at both timepoints. Specifically, the ACC group exhibited lower activity and approach dimensions of positive emotionality at both timepoints, with lower high-intensity pleasure at 6 months and lower vocal reactivity at 12 months. On negative emotionality subscales, the ACC group exhibited lower distress to limitations and sadness at both timepoints, as well as lower falling reactivity at 6 months. The ACC and HL groups did not differ significantly on positive emotionality at either timepoint. However, negative emotionality was lower in the ACC group than the HL- group at both timepoints and lower than the HL+ group at 12 months, with lower distress to limitations and sadness ratings than both HL groups at both timepoints.

These findings highlight the importance of interhemispheric connections in facilitating active engagement and pursuit of pleasurable activities during the first year of life, as well as expression of sadness and distress to limitations. Notably, similarities between infants with ACC and infants at elevated familial risk of ASD suggest that disrupted callosal connectivity may specifically contribute to reductions in positive emotionality.

It is unclear how agenesis of the corpus callosum (ACC), a congenital brain malformation defined by complete or partial absence of the corpus callosum, impacts language development. fMRI studies of middle childhood suggest that the corpus callosum plays a role in the interhemispheric language network (Bartha-Doering et al., 2020), and that reduced interhemispheric functional connectivity is correlated with worse language abilities in children with ACC (Bartha-Doering et al., 2021). Additionally, accumulating evidence suggests structural abnormalities of the corpus callosum play a role in neurodevelopmental disorders. While children who go on to receive an autism spectrum disorder (ASD) diagnosis may show early signs of altered word and gesture acquisition (Iverson et al., 2018), the same is not known about ACC. This study examined language development during the second year of life in children with ACC in comparison to neurotypical control participants, as well as other children at elevated risk of ASD.

The MacArthur-Bates Communicative Development Inventories (MCDI): Words and Gestures scales were administered to parents of 74 children with isolated ACC at 12, 18 and 24 months of age. Children whose first language was not English and children who were bilingual were excluded. Comparison groups consisted of individuals with a low familial likelihood of ASD (LL- n=140) and individuals with high familial likelihood of ASD who do and do not have a confirmed ASD diagnosis (HL+ n=68, HL- n=256).

Compared to LL controls, the ACC group produced fewer words at 18 and 24 months of age, and demonstrated fewer words understood at all three timepoints. Similarly, compared to the HL- group, the ACC group demonstrated fewer words produced and understood at 18 months of age, and fewer words produced at 24 months of age. The ACC and HL+ groups did not differ in words produced or words understood at any timepoint.

Overall, infants with ACC demonstrated delayed vocabulary expansion from 12 to 24 months of age. These findings illustrate the role of callosal connectivity in the development of language across the first 2 years of life, and highlight the need for support and interventions that target vocabulary production and comprehension.

Differences in adaptive functioning present early in development for many children with monogenic (Down Syndrome, Fragile X) and neurodevelopmental disorders. At this time, it is unclear whether children with ACC present with early adaptive delays, or if difficulties emerge later as functional tasks become more complex. While potential delays in motor development are frequently reported, other domains such as communication, social and daily living skills are rarely described. We used a prospective, longitudinal design to examine adaptive behavior from 6-24 months in children with ACC and compared their trajectories to those with monogenic and neurodevelopmental conditions.

Our sample included children with primary ACC (n= 27-47 depending on time point) whose caregivers completed the Vineland Adaptive Behavior Scales-Interview 3rd Edition, via phone at 6, 12, 18 and 24 months. Comparison samples (using the Vineland-2) included children with Down Syndrome (DS; n = 15-56), Fragile X (FX; n = 15-20), children at high familial likelihood for autism (HL-; n=192-280), and low likelihood (LL; no family history of autism and no developmental/behavioral diagnosis; n = 111196). A subset of the HL children received an autism diagnosis (HL+; n = 48-74). The DS group did not have an 18-month Vineland.

A series of linear mixed model analyses (using maximum likelihood) for repeated measures was used to compare groups on three Vineland domains at 6, 12, 18 and 24 month timepoints). All fixed factors (diagnostic group, timepoint, and group X timepoint interaction) accounted for significant variance on all Vineland domains (p < .001). Post hoc comparisons with Bonferroni-correction examined ACC Vineland scores compared to the other diagnostic groups at each timepoint. At 6 months, parent-ratings indicated the ACC group had significantly weaker skills than the LL group in Communication and Motor domains. At 12, 18 and 24 months, ratings revealed weaker Communication, Daily Living and Motor skills in the ACC group compared to both the LL and HL- groups. Compared to the other clinical groups, the ACC group had stronger Socialization and Motor skills than Fragile X at 6 months, and at 24 months had stronger Communication and Socialization skills than both the DS and FX groups, as well as stronger Socialization than the HL+ group.

Compared to children with low likelihood of ASD, children with primary ACC reportedly have weaker Communication and Motor skills from 6 to 24 months, with weakness in Daily Living Skills appearing at 12 months and all differences increase with age. Compared to Fragile X, the ACC exhibited relative strengths in socialization and motor skills starting at 6 months. By 24 months, the ACC group was outperforming the monogenic groups on Socialization and Communication. In general, the ACC scores were consistent with the HL+ sample, except the ACC group had stronger Social skills at 18 and 24 months. The results clearly inform the need for early intervention in the domains of motor and language skills. Additionally, as we know that children with ACC are at increased risk for social difficulties, research is needed both using more fine-grained social-communication tools, and following children from infancy through middle childhood.

Poor air quality is associated with poor health. Little attention is given to the complex array of environmental exposures and air pollutants that affect mental health during the life course.

We gather interdisciplinary expertise and knowledge across the air pollution and mental health fields. We seek to propose future research priorities and how to address them.

Through a rapid narrative review, we summarise the key scientific findings, knowledge gaps and methodological challenges.

There is emerging evidence of associations between poor air quality, both indoors and outdoors, and poor mental health more generally, as well as specific mental disorders. Furthermore, pre-existing long-term conditions appear to deteriorate, requiring more healthcare. Evidence of critical periods for exposure among children and adolescents highlights the need for more longitudinal data as the basis of early preventive actions and policies. Particulate matter, including bioaerosols, are implicated, but form part of a complex exposome influenced by geography, deprivation, socioeconomic conditions and biological and individual vulnerabilities. Critical knowledge gaps need to be addressed to design interventions for mitigation and prevention, reflecting ever-changing sources of air pollution. The evidence base can inform and motivate multi-sector and interdisciplinary efforts of researchers, practitioners, policy makers, industry, community groups and campaigners to take informed action.

There are knowledge gaps and a need for more research, for example, around bioaerosols exposure, indoor and outdoor pollution, urban design and impact on mental health over the life course.

International best-practice guidelines for the management of first-episode psychosis have recommended the provision of psychoeducation for multifamily groups. While there is ample evidence of their efficacy in multiepisode psychosis, there is a paucity of evidence supporting this approach specifically for first-episode psychosis. We sought to determine whether a six-week caregiver psychoeducation programme geared specifically at first-episode psychosis improves caregiver knowledge and attitudes.

Caregivers of people with first-episode psychosis completed a 23-item adapted version of the self-report Family Questionnaire (KQ) and a 17-item adapted version of the self-report Drug Attitudes Inventory (DAI) before and after the six-week DETECT Information and Support Course (DISC). Using a Generalised Linear Repeated Measures Model, we analyzed the differences in proportions of correct answers before and after the programme.

Over a 24-month study period, 31 caregivers (13 higher socioeconomic; 13 lower socioeconomic; five unspecified socioeconomic; 19 female; 12 male) participated in the DISC programme and completed inventories before and after the course. Knowledge of psychosis and specific knowledge of medication treatment improved among caregivers overall (p < .01; effect sizes 0.78 and 0.94 respectively). There were no significant gender or socioeconomic differences in any improvement.

This study confirms that caregiver psychoeducation specifically for first-episode psychosis directly improves knowledge of the illness overall and, in particular, knowledge of medication. Gender is not a factor in this, while the lack of any socioeconomic differences dispels the myth that patients in lower socioeconomic groups are disadvantaged because their caregivers know less.