Biomarkers – detailed findings Discovery, validation of biomarkers of mental health, and linkage to exposures

Level of evidence	Direct evidence from analysing biosamples in two child cohorts – Walnuts (Spain) and FinnTwin (Finland)
Approach	Preliminary biomarker discovery in the Walnuts cohort: ·      We analysed plasma proteomic and bioinformatic data and identified significant changes in several proteins by comparing low- and high-risk groups, based on SDQ scores. (de Sousa Maciel et al. 2023). ·      We carried out further analyses for the entire sample set of 198 Walnuts plasma using linear modelling, to identify proteomic biomarkers associated with the SDQ score. We investigated the linear association of proteins with the full SDQ score, as well as with externalising and internalising sub-scores. (Alatalo, 2023) Biomarker studies using the FinnTwin12 cohort: ·      We compared the protein-based biomarkers identified in the Walnuts cohort with those in the larger FinnTwin12 cohort. We identified potential biomarkers in subjects with high or low risk for mental health dysfunction based on the p-factor. There was very little overlap with the Walnuts study results (Afonin et al, 2024). Linking biomarkers to exposures: ·      In Walnuts and FinnTwin12, we first evaluated the associations between the mid-adolescent external exposome and plasma proteomic biomarkers of mental health with two types of exposome-wide proteome-wide analyses: multivariate Bayesian model relationship and Exposome-Wide Association Study (ExWAS) for each protein for the one-to-one relationship.  ·      We then explored the “mediation” role of omics biomarkers of mental health in the relationship between the exposome and life satisfaction in adolescents and young adults (Wang et al)
Findings	Equal-Life research discovered initial potential biomarkers of child mental health. However, no common biomarkers were found between cohorts, so further replication studies are needed to validate these biomarkers. Current findings are insufficient to inform public health policies, such as recommending early biomarker screening – which would require stronger evidence, ethical assessments, and awareness of the risks of medicalizing childhood. Specific findings include: ·      Mid-adolescence exposures (lifestyle, indoor quality, natural and social environments) are linked to proteomic biomarkers. (Wang et al) ·      Plasma proteomic and metabolomic analyses in two cohorts linked biomarkers to mental health indicators (e.g., SDQ, depression, aggression) Findings are inconsistent between cohorts, necessitating further replication with standardized protocols. (Wang et al) ·      Branched chain amino acids are associated with depression in young adults from the FinnTwin12 study (Whipp et al, 2022). ·      Ketone body 3-hydroxybutyrate is a metabolite associated with aggression. The association is replicated in an independent Dutch sample. (Whipp et al, 2021). ·      Greenspaces influenced biomarkers in both cohorts, but individual biomarkers explained only weak correlations with mental health, emphasizing the role of genetic-environment interactions. ·      Lower similarity in co-twins' exposome profiles corresponded to behavioral differences, particularly excessive drinking tied to external exposome, showing social behavior links to internal/external exposome, as shown in the FinnTwin12 cohort (Drouard et al, 2024) ·      The proteome is associated with obesity in adolescence and young adulthood in the FinnTwin12 cohort and replicated in the Netherlands Twin Registry. Obesity is a risk factor for poor mental health and should be included in internal exposome analyses (Drouard et al, 2024) ·      Social neighborhood exposome modestly affects late adolescent mental health. Growth factors (e.g., proportion of childless households) are linked to internalizing problems in females. Addressing social inequalities may improve the outcomes.
Recommendations	For researchers: ·      Conduct collaborative, multi-site studies with standardised methodologies to discover associations between exposome factors, biomarkers, and mental health.
Target audience:	Researchers, ethicists
Scientific publications:	Plasma proteomics discovery of mental health risk biomarkers in adolescents. (de Sousa Maciel, I., Piironen, AK., Afonin, A.M. et al.) Nat. Mental Health 1, 596–605 (2023). https://doi.org/10.1038/s44220-023-00103- Proteomic insights into mental health status: plasma markers in young adults. (Afonin, A.M., Piironen, AK., de Sousa Maciel, I. et al.) Transl Psychiatry 14, 55 (2024). https://doi.org/10.1038/s41398-024-02751-z Branched-chain amino acids linked to depression in young adults frontiers. (Alyce M. Whipp, Marja Heinonen-Guzejev, Kirsi H. Pietiläinen, Irene van Kamp, Jaakko Kaprio). Frontiers in Neuroscience (2022). https://doi.org/10.3389/fnins.2022.935858 Whipp AM, Vuoksimaa E, Korhonen T, Pool R, But A, Ligthart L, Hagenbeek FA, Bartels M, Bogl LH, Pulkkinen L, Rose RJ, Boomsma DI, Kaprio J. Ketone body 3-hydroxybutyrate as a biomarker of aggression. Sci Rep. 2021 Mar 12;11(1):5813. doi: 10.1038/s41598-021-84635-6. PMID: 33712630; PMCID: PMC7955062. Lifestyle differences between co-twins are associated with decreased similarity in their internal and external exposome profiles. (Drouard G, Wang Z, Heikkinen A, Foraster M, Julvez J, Kanninen KM, van Kamp I, Pirinen M, Ollikainen M, Kaprio J.) Sci Rep 14, 21261 (2024). https://doi.org/10.1038/s41598-024-72354-7 Associations between the mid-adolescent external exposome and proteomic biomarkers of mental health. (Zhiyang Wang, Gabin Drouard, Aleksei Afonin, Núria Botella, Carmen Peuters, Aino-Kaisa Piironen, Alyce. M. Whipp, Boris Cheval, Libor Šulc, Marja Heinonen-Guzejev, Maria Foraster, John Gulliver, Jenny Selander, Payam Dadvand, Jordi Júlvez, Irene van Kamp, Katja M. Kanninen, Jaakko Kaprio, Equal-Life Scientific Team) Preprint medRxiv (2024) https://doi.org/10.1101/2024.12.18.24319208 The Interaction between Circulating Cell-Free Mitochondrial DNA and Inflammatory Cytokines in Predicting Human Mental Health Issue Risk in Adolescents: An Explorative Study. (Alatalo A, de Sousa Maciel I, Kucháriková N, Chew S, van Kamp I, Foraster M, Julvez J, Kanninen KM) An Explorative Study. Biomedicines (2023) https://doiorg/10.3390/biomedicines11030818 Drouard G, Hagenbeek FA, Whipp AM, Pool R, Hottenga JJ, Jansen R, Hubers N, Afonin A; BIOS Consortium, BBMRI-N. L. Metabolomics Consortium; Willemsen G, de Geus EJC, Ripatti S, Pirinen M, Kanninen KM, Boomsma DI, van Dongen J, Kaprio J. Longitudinal multi-omics study reveals common etiology underlying association between plasma proteome and BMI trajectories in adolescent and young adult twins. BMC Med. 2023 Dec 21;21(1):508. doi: 10.1186/s12916-023-03198-7. PMID: 38129841; PMCID: PMC10740308.