[Social media and teenagers' mental health]. / Médias sociaux et santé mentale des adolescents.

SOCIAL MEDIA AND TEENAGERS' MENTAL HEALTH. Social media are widely used daily especially amongst adolescents. The fast apparition and evolution of these platforms might be difficult to follow. Social Media can expose to risks that it is important to be aware of, in order to assess in clinical practice their impact on adolescents' health and to be able to provide useful guidance. After recalling what social media are and their characteristics, and giving the latest statistical data available, the problems encountered on them according to young people as well as their positive effects are exposed. The risks of using these media often described in literature are then discussed. Recommendations exist for health professionals, parents and adolescents regarding these issues, as well as many websites suggesting practical ways to promote a healthy use of social media.

MÉDIAS SOCIAUX ET SANTÉ MENTALE DES ADOLESCENTS. L'utilisation des médias sociaux est omniprésente au quotidien et en particulier chez les adolescents. La rapidité d'apparition et d'évolution de ces plateformes peut être difficile à suivre. Or les médias sociaux exposent à certains risques, qu'il est important de connaître afin de pouvoir évaluer en pratique clinique leurs impacts sur la santé des adolescents et fournir des conseils adaptés. Après avoir rappelé ce que sont les médias sociaux et leurs caractéristiques, et précisé les dernières données statistiques disponibles, les problèmes rencontrés sur ces derniers d'après les jeunes ainsi que leurs effets positifs sont exposés. Les risques de l'utilisation de ces médias couramment évoqués dans la littérature sont ensuite discutés. Des guides pour l'évaluation et des recommandations existent, à destination des professionnels de santé, des parents et des adolescents ; de nombreuses ressources en ligne proposent des idées pour favoriser un usage sain des médias sociaux.

Maternal immune activation during pregnancy is associated with more difficulties in socio-adaptive behaviors in autism spectrum disorder.

Autism spectrum disorder (ASD) are neurodevelopmental conditions characterised by deficits in social communication and interaction and repetitive behaviours. Maternal immune activation (MIA) during the mid-pregnancy is a known risk factor for ASD. Although reported in 15% of affected individuals, little is known about the specificity of their clinical profiles. Adaptive skills represent a holistic approach to a person's competencies and reflect specifically in ASD, their strengths and difficulties. In this study, we hypothesised that ASD individual with a history of MIA (MIA+) could be more severely socio-adaptively impaired than those without MIA during pregnancy (MIA-). To answer this question, we considered two independent cohorts of individuals with ASD (PARIS study and FACE ASD) screened for pregnancy history, and used supervised and unsupervised machine learning algorithms. We included 295 mother-child dyads with 14% of them with MIA+. We found that ASD-MIA+ individuals displayed more severe maladaptive behaviors, specifically in their socialization abilities. MIA+ directly influenced individual's socio-adaptive skills, independent of other covariates, including ASD severity. Interestingly, MIA+ affect persistently the socio-adaptive behavioral trajectories of individuals with ASD. The current study has a retrospective design with possible recall bias regarding the MIA event and, even if pooled from two cohorts, has a relatively small population. In addition, we were limited by the number of covariables available potentially impacted socio-adaptive behaviors. Larger prospective study with additional dimensions related to ASD is needed to confirm our results. Specific pathophysiological pathways may explain these clinical peculiarities of ASD- MIA+ individuals, and may open the way to new perspectives in deciphering the phenotypic complexity of ASD and for the development of specific immunomodulatory strategies.

Age-structured cell population model to study the influence of growth factors on cell cycle dynamics.

Cell proliferation is controlled by many complex regulatory networks. Our purpose is to analyse, through mathematical modeling, the effects of growth factors on the dynamics of the division cycle in cell populations. Our work is based on an age-structured PDE model of the cell division cycle within a population of cells in a common tissue. Cell proliferation is at its first stages exponential and is thus characterised by its growth exponent, the first eigenvalue of the linear system we consider here, a growth exponent that we will explicitly evaluate from biological data. Moreover, this study relies on recent and innovative imaging data (fluorescence microscopy) that make us able to experimentally determine the parameters of the model and to validate numerical results. This model has allowed us to study the degree of simultaneity of phase transitions within a proliferating cell population and to analyse the role of an increased growth factor concentration in this process. This study thus aims at helping biologists to elicit the impact of growth factor concentration on cell cycle regulation, at making more precise the dynamics of key mechanisms controlling the division cycle in proliferating cell populations, and eventually at establishing theoretical bases for optimised combined anticancer treatments.