IntroductionSuicide is a major public health problem. The objective of this study is to analyze the demographic, clinical and toxicological characteristics and the mechanisms of suicide in young people and middle-aged adults. MethodRetrospective population study of completed suicide in subjects aged 14-55 who were subjected to a forensic autopsy in Bizkaia between 2016-2018. Results272 suicides were recorded. The global incidence was 7.8/100.00 inhabitants/year. 127 were 14-55 years old. The rate was 3 times higher in men and increased with age. In 72%, some clinical risk factor was collected, mainly mental disorders (59%): mood disorders (23%), substance abuse (20.5%) and psychotic disorders (14%). 38% of addicts had another mental disorder. Physical illness (23%) and suicide attempt (20.5%) were also relevant factors. 41% were positive for alcohol and/or illicit drugs: ethanol (22%), cannabis (16%), cocaine (11%) and amphetamine (8%). This percentage was 79% in substance addicts. Substance abuse disorders (25% vs. 6.5%; p = 0.03) and presence of alcohol and/or drugs (49% vs. 16%; p = 0.001) were more prevalent in men. The most commonly used methods were fall from heights (35%) and hanging (31%). ConclusionsThe incidence of suicide in Bizkaia is lower than the European average. Suicide is a complex problem associated with demographic and clinical factors (mainly depressive and substance abuse disorders) and recent use of alcohol and illicit drugs. Prospective multidisciplinary and multicenter researches are required in order to identify risk factors and to guide preventive measures.