To investigate the relationship between heavy daily smoking and suicidality among adolescent psychiatric inpatients in Finland.

Data were collected from 411 patients (age 12–17 years) admitted to inpatient psychiatric hospitalization between April 2001 and July 2005. The number of daily cigarettes (>15) and the time of first cigarette after waking up (within 30 min) were used as indicators of heavy daily smoking.

After adjusting for psychiatric diagnoses an over twofold risk for suicide attempts was found among adolescents who smoked over 15 cigarettes a day. Additionally, if an adolescent also smoked the first cigarette immediately after waking up the risk was over threefold. Suicidal ideation was not associated with smoking behaviour.

Among adolescents with severe psychiatric illnesses, heavy daily smoking may increase the risk of suicidal behaviour independently of current psychiatric diagnosis. The degree of nicotine dependence of an adolescent should therefore be carefully assessed as part of psychiatric evaluation.

Despite of higher rates of substance-related disorders in psychiatric patients and suicides than in the general population, there is no clear specificity to the relationship between nicotine use and other psychiatric disorders for suicide risk.

One hundred and sixty-three suicides (mean age 49.8 ± 19.3 years; 64.4% males; using psychological autopsy method) and 396 control persons (mean age 51.6 ± 17.0 years; 55.8% males) were assessed with a standardised semi-structured interview including SCID-I and SCID-II (for DSM-IV). Suicides and controls were compared in terms of nicotine consumption and psychiatric disorders. Logistic regression was used to evaluate the interactions of tobacco consumption with psychiatric disorders.

Suicides were significantly more often current smokers and heavy users of cigarettes (>20 cigarettes per day; P < 0.001, each). Alcohol dependence, other axis I disorders than substance-related disorders, and cluster B personality disorder(s) remained independent predictors for suicide in both genders, current nicotine consumption only in men (OR = 2.6, 95% CI 1.3–5.2).

In males, but not in females, nicotine consumption contributed to risk of completed suicide after control for psychiatric disorders and has to be considered as independent risk factor for suicide.