Abstract patterns of mental disorders and suicidal behavior, and concordance in monozygotic adult twins: a decade-long prospective study

Brief Introduction: Genetic factors, in interaction with environmental influences, play a significant role in the development of mental disorders, and suicidal behavior could be explained by a more and broad complex and dynamic interaction of both factors (1). Suicide ideation, suicide attempt and complete suicide, are significantly heritable phenotypes. Also, there are higher concordance rates for suicide in monozygotic twins compared to dizygotic twins (2) (3). The identification of genes that place people at risk of suicide is yet elusive, although data describe Tryptophan hydroxylase (TPH), specially TPH1 and TPH2, associated with suicide in various publications (4), even though there are several papers referring to polymorphisms on involved genes. On the other hand , there is a publication of similar studies made by authors on twins, so it constitutes an additional study with a greater number of probands.

Aims: This study aimed to investigate the prevalence and gender-specific patterns of mental disorders and suicidal behavior and also concordance in monozygotic adult twins along a decade.

Methods

: A prospective and descriptive study was conducted from 2015 to 2025 at the National Institute of Mental Health, in Emergency and Adults Departments .Participants, rigorously selected, twins , aged 18 to 89 years old, were diagnosed according to WHO- ICD-10 clinical criteria for mental disorders, and Scales for several of these (Mood Disorder Questionnaire, Beck Depression Inventory and Beck Anxiety Inventory , Positive and Negative Syndrome Scale for Schizophrenia, as well as Pierce Suicide Intent Scale for Suicidal Risk Assessment) were applied.

Summary

: Thirty four pairs (34) of monozygotic twins were identified: 9 male pairs (26.5 %) and 25 female pairs (73.5 %). Diagnoses included : Bipolar Disorder in 12 pairs (35.3%), Major Depressive Disorder in 11 pairs (32.3 %), Anxiety Disorder in 5 pairs (14.7%), Schizophrenia in 4 pairs (11,8 %), and , other Disorders in 2 pairs (5.9 %). In regard to concordance for suicidal behavior in both co-twins : for Bipolar Disorder (0.40), Depressive Disorder (0.26),Anxiety Disorder (0.13), Schizophrenia (0.13), and others (0.06). Suicidal behavior was more prevalent amongst female twins in Bipolar and Depressive Disorders, with gender variations for other disorders.

Conclusions

: This ten-year study highlights the predominance of Bipolar and Depressive Disorders and also suicidal behavior concordance amongst female monozygotic twins, specially for former, as reported in previous article by same authors, and distinct gender-specific patterns for other disorders. The findings underscore the importance of strong influence of genetic factors over suicidal behavior mostly in bipolar and depressive monozygotic twins, and could reinforce genetic dimension about sahring genes or inheritance in case of phenotype of closed relative probands. It is a pending task for our researchers the respective identification of genes in studied sample,requiring Genetic facilities and an adequate budget

References

References: : 1.-Lim KX, Krebs G, Rimfeld K, Pingault JB, (2022) Investigating the genetic and environmental aetiology of non-suicidal and suicidal self-harm: a twin study, 2022-cambridge-org 2.-Pedersen NL, Fiske A, (2010) Genetic influences on suicide and non-fatal suicidal behavior: twin study findings ,2010-cambridge.org 3.-Juli G, Juli A, Juli L, (2024) The Correlation between genetics and suicidal behaviors: a challenge of Literature. 2024-hrcak.srce.hr 4.- Khalil, M.; Kalyoncu, A.; Bellon, (2025) A. Genetics of Suicide. Genes,2025, 16, 428. https://doi.org/10.3390/genes16040428