Suicide can be defined as the voluntary and intentional ending of one's life, the act of taking one's own life. Suicide, a major public health threat; It is a complex set of actions ranging from suicidal ideation to suicide attempt and completed suicide. suicidal tendency; The phenomenon of suicide is the subject of a multidisciplinary research field because of the effect of a biopsychosocial and integrated factor group, including biological/genetic, psychological and sociological (social conditions and stress factors).
It is known that approximately 1 million people commit suicide every year around the world, and studies show that suicide deaths, which are among the top 10 causes of death, constitute 1.5% of all deaths; It shows that it has an important place among the causes of death in the 15-44 age group.
Genetic Basis of Suicide
Conducted under the headings of genetic and epidemiological research in order to elucidate the neurobiological (neuroscience) mechanisms of suicidal behavior; Supportive evidence from family, twin, and adoption studies is a strong indication that "genetics also plays a role in suicidality." family studies; revealed that the intrafamilial risk in suicide, that is, genetic transmission through risk-candidate genes that may be responsible for this behavior among family members, shows a familial clustering compared to the risk in the general population. In twin studies; Genetic and environmental factors have been evaluated between monozygotic (identical) and dizygotic (fraternal) twins, and it has been reported that the risk of suicide is higher in monozygotic twins.
Within the scope of adoption studies, in order to evaluate genetic and environmental factors, evaluations were made on siblings who grew up in the same environment and with their biological family, biological siblings who were separated immediately after birth, and their biological and non-biological (adoptive) families. In the results obtained, the genetic susceptibility of the biological families of adopted children was observed, contributing to other results.
For many years, these studies reversed the idea that suicidal behavior is caused by mood disorders in the person and his family. The results did not exclude the fact that psychiatric disorders alone have a partial effect and increase on suicidality; .
The genetic basis of suicide has been proven by identifying and investigating possible genes. Because the epigenetic response of the genome to environmental effects completes the complex genetic phenotype of suicide. In recent years, with the development of technology, great progress has been made in cytogenetic and molecular genetic studies to determine the role of genetic factors. With cytogenetic studies, it is determined in which chromosome band the suicidal candidate genes are located, and gene maps are made over the broken points in the chromosomes. Molecular genetic studies, on the other hand, are used intensively to identify candidate/risk genes to cause suicide with DNA methylation, histone modifications, disruption of gene expression and linkage imbalance approaches.
Molecular genetic studies are based on the principle of detecting gene polymorphisms by determining the nucleotide sequences of candidate genes. Although PCR (polymerase chain reaction) and RFLP (restriction fragment length polymorphism) methods are frequently used in studies, candidate-gene association analyzes in which single nucleotide polymorphisms (SNP-single nucleotide polymorphism) are mostly used is done.
Candidate gene association analyzes are performed to identify gene variations that lead to complex phenotypes such as suicide. These studies are of great importance in identifying protective and risk factor polymorphic variants and are still the most popular method for examining genetic factors of suicide.
Neurobiology of Suicide
Studies conducted in the last three decades have shown that a number of neurobiological pathways are responsible for suicidal behavior and its etiology. These neurobiological pathways such as Serotonergic, Dopaminergic, Noradrenergic, GABAergic or Neuroimmune Systems and the genes, diseases or endophenotypes (biological markers/signs indicating disease susceptibility) associated with their dysfunction have been the subject of study primarily.
Deregulation of monoaminergic transmitter systems such as norepinephrine, dopamine and serotonin, neurotransmitter system inhibitor GABA, glutamatergic excitatory system, neurotrophic signaling factors, cannabinoid system, lipid metabolism and HPA axis (hypothalamus-pituitary-adrenal axis) are considered as risky and possible causes in the neurobiology of suicide.
As suicidal candidate genes; Studies have been carried out on dopaminergic, adrenergic system receptors and genes/gene expressions responsible for the regulation of mostly serotonergic neurotransmission. Among these; Serotonin metabolism genes (TPH), serotonin transport (5-HTT) and serotonin receptor (5-HTR) genes are the ones that draw the most attention in studies.
Serotonin (5-hydroxytryptamine; 5-HT); It is a defined neurotransmitter in vascular smooth muscle, gastrointestinal tract, and brain. These biological amines, which are known to have important functions in the central nervous system, have a key role. In postmortem (Type: "post-mortem") studies; It has been reported that low serotonin activity and serotonergic dysfunction in the orbital prefrontal cortex of the brain increase the incidence of death from suicide, and are also associated with a tendency to impulsive and aggressive behaviors.
Conclusion
As a result; With these gene-level studies to make sense of the genome's epigenetic response to environmental effects, increasing evidence for the genetic basis of suicide has been presented, but specific biomarkers have not yet been determined. There is a need for new and more advanced neurobiology studies with large samples and excluding factors that would reduce the reliability of the result. Thus; First of all, suicide attempts will be determined and prevented, and on the other hand, in suicide cases that end in death, the origin of the event and the investigation will gain depth.