Suicidal behaviour: genes, environmental stress and temperamental traits Temperamental traits of impulsive aggression, neuroticism and introversion have also been implicated in suicidal risk. However, it is unlikely that these factors, themselves, can explain suicide. As regard genetic effects, suggestive evidence has been reported for serotonin transporter gene (SLC6A4), serotonin receptor 2A (5HTR2A), Tryptophan hydroxylase (TPH1, TPH2), Cathechol- o-methyl tranferase (COMT) and Brain derived neurotrophic factor (BDNF). Other interesting genes are dopamine receptor D2 (DRD2), Cortico-trophin- releasing hormone 1 (CRHR1). Studies addressed to investigate the combined effect of genetic predisposition and environmental influences reported positive findings for SLC6A, 5HTR2A, BDNF and Regulator of G-protein sig- naling 2 (RGS2). Finally, among genes influencing suicide-related traits, the Mono-amine oxidase A (MAOA) and the COMT showed interactive effects with early adverse events on impulsivity and anger in suicidal individuals. In con- clusion, there is evidence of a genetic liability for suicidal behaviour, be modu- lated by environmental risk factors as well as individual psychological charac- teristics, such as temperamental traits. Future studies are required to address this complexity by an integrated approach. Key words: suicide, life events, child- hood trauma, temperamental traits, gene, gene-environment interaction. Introduction Suicide or suicide completion is the act of taking one's own life voluntarily. Suicide-related behaviour is a general term used to refer to self-injury, suicide attempt and suicide. According to Silver- man et al. (2007), self-injury with no or undetermined intent to die refers to “self-harm” and “undetermined suicide- related behaviour” respectively. When clear or some degree of intent to die is present, we refer to “suicide attempt” when self-harm does not result in death and “suicide” when it has a fatal outcome Suicide-related ideations and communi- cations with some intent to die (suicidal threat and suicidal plans) may be also present independently from manifest self-destructive acts. Suicide is a major public health problem, representing the 10th leading cause of death worldwide (Levi et al., 2003). The incidence rate for completed suicide vary considerable in different countries, from 1.1 per 100,000 inhabitants in Azerbai- jan to 51.6 per 100,000 inhabitants in Lithuania (WHO, 2002). The highest suicide rates are found in Eastern Euro- pean countries (Belarus, Estonia and Lithuania and Russian federation); low rates are found mainly in Latin America (Colombia, Paraguay) and some coun- tries in Asia (Philippines and Thailand 5.6), while Countries in other parts of Europe, in North America, and parts of Asia and the Pacific tend to fall somewhere in between these extremes (as examples: Finland 28.4/ 100,000, France 20.0/ 100,000, USA 13.9/100,000). According to the World Health Organization (WHO) World Mental Health (WMH) Surveys (conducted 2001–2007); the 12-months prevalence estimate of suicide attempts is 0.3% (Borges et al., 2010). In most countries, men have a higher reported rate of completed suicide, whereas women have a higher rate of attempted suicide (Schmidtke et al., 1996). Suicide rates are highest in elderly people in most countries. However, over the past 50 years, rates have risen in young people, in particular in men (Wasserman et al., 2005; Wasserman & Wasserman, 2009), and decreased in elderly people (Pritchard & Hansen, 2005). Over 90% of suicides had recognizable psychiatric illness at the time of their death (Tanney, 2000), mostly mood disorders, borderline personality disorder, post-traumatic stress disorder and schizo- phrenia (Bolton & Robinson, 2010). Nevertheless, the association between suicide and psychiatric disorders is not linear, therefore independent risk factors should account for the individual risk for suicide. In the present article we aimed to re- view the current knowledge of genetic factors involved in suicidal behaviours, in particular completed suicide and suicide attempt, and their interaction with environmental risk factors. More- over, we also took into account the few studies addressing the interplay between genetic predisposition, suicide-related temperamental traits and suicidal risk. Methods Literature search Genetic studies in suicidal behaviour were located through several literature- search strategies. Up to March 2011, appropriate search terms (gene, genetics, 3 18 SUICIDOLOGI 2011, ÅRG. 16, NR. 2 By Laura Mandelli 1 , Vladimir Carli 2-3 , Alessandro Serretti 1 and Marco Sarchiapone 2 Suicidal behaviour: genes, environmental stress and temperamental traits Genetics and gene-environment interaction in suicide. 1 Institute of Psychiatry, University of Bologna, Bologna, Italy, 2 Department of Health Sciences, University of Molise, Campobasso, Italy 3 National Prevention of Suicide and Mental Ill-Health (NASP), Karolinska Institutet, Stockholm, Sweden ABSTRACTS: Multiple risk factors have been involved in the risk for suicide and multiple trajectories have been hypothesized leading to suicidal behaviour. Consistent evidence suggests the involvement of heritable factors, as well as a critical role of life stress and early adversity. In the present article we will review the evidence for the involvement of genetic, environmental as well as personality traits in the risk for suicide, together with recent evidence supporting an interaction between these different factors.