4.1. Suicidal behaviour and substance use disorders

The contribution of alcohol and other substances to completed suicides and suicide attempts is complex and appears to constitute effects ranging from psychosocial disruption to disinhibited and dysphoric states of mind and choice of suicide method (Tamerin & Mendelson 1969, Mayfield et al 1972, 1979, Roy & Linnoila 1986, APA 1995, Schuckit et al 1995, 1998, Öhberg 1998). Murphy and Wetzel (1990) estimated that 2% to 3.4% of alcohol dependent subjects in the general population commit suicide. According to a recent meta-analysis of mortality studies, the lifetime risk for suicide is 7% in alcohol dependence (Inskip et al 1998). The standardised mortality ratio (SMR) to suicide is estimated at 586 (95% CI 541-633) for DSM-III-R alcohol dependence and abuse (Harris & Barraclough 1997).

In inpatient population studies alcohol and other substance use disorders have independently associated with suicidal ideation (Pages et al 1997, Hall et al 1998). However, the comorbidity of psychiatric disorders among alcohol dependent subjects reportedly relatively more important than the alcohol dependence for the suicidal risk (Driessen et al 1998). Cornelius et al (1995) studied patients in an urban psychiatric inpatient and outpatient psychiatric facility and found differences between depressive alcoholics, nonalcoholic depressives and nondepressed alcoholics. Depressed alcoholics had significantly higher suicidality than subjects with either depression or alcohol dependence. The authors suggested that alcohol dependence and depression act additively or synergistically, resulting in a disproportionate suicide risk among subjects with both disorders (Cornelius et al 1995).

Among adolescents alcohol use and abuse per se are known to associate with aggressive and impulsive behaviour, dysphoric mood, and - among alcohol abusers - suicide risk (Milgram 1993, Bukstein et al 1993). Abuse of or dependence on alcohol and other psychoactive substances among adolescents is often associated with multiple psychosocial problems, psychiatric comorbidity, suicidal ideation, suicide attempts (Berman & Schwartz 1990, Deykin et al 1994, Beautrais et al 1996, Weinberg et al 1998), and completed suicide (Brent et a 1988, Allebeck & Allgulander 1990, Shaffer et al 1996). Longitudinal studies of adolescent psychiatric patients and suicide attempters have found alcohol and drug abuse to be one of the major risk factors for suicide (Östman 1991, Hawton et al 1993). Substance use disorders along with other psychopathology, sociodemographic disadvantage and adverse childhood experiences are also reportedly associated with risk of serious suicide attempts among adolescents (Beautrais et al 1996).

4.2. Alcohol and other substance use disorders in completed suicide

4.2.1. Psychoactive substance use diagnoses in psychological autopsy studies

In most psychological autopsy studies more than 90% of the suicide victims have suffered from mental disorders, affective and addictive disorders being the most frequent (Robins et al 1959, Dorpat et al 1960, Barraclough et al 1974, Beskow 1979, Hagnell et al 1979, Chynoweth et al 1980, Mitterauer 1981, Shafii et al 1985, 1988, Rich et al 1986, Arato et al 1988, Brent et al 1988, Runeson 1989, Åsgård 1990, Conwell et al 1991, Marttunen et al 1991, Apter et al 1993, Henriksson et al 1993, Brent et al 1993, Lesage et al 1994, Cheng 1995, Conwell et al 1996, Shaffer et al 1996, Foster et al 1997). In unselected suicide populations alcohol abuse or dependence is retrospectively found among 15-56% of victims (Table 3). Comorbidity is common in suicide populations (Henriksson et al 1993, Cheng 1995, Conwell et al 1996, Foster et al 1997) and the highly prevalent substance use disorders and their comorbidity patterns are of considerable importance and interest.

Table 3. Psychological autopsy studies

In the San Diego Study, Rich and colleagues suggested that substance abuse was a major contributor to increase in young people's suicides (Rich et al 1986). In this psychological autopsy study they found no significant differences in the rates of substance abuse between men and women, but significantly more diagnoses of drug abuse among the cases aged under 30 than in those aged 30 and over. Substance abuse appeared to be more important in the etiology of suicides in their study than had been previously believed (Rich et al 1989).

Within the Nationwide Suicide Prevention Project in Finland, a study of unselected suicides (Henriksson et al 1993) found more alcohol use disorders than in most previous studies. The prevalence of alcohol dependence among males was higher than observed elsewhere, but female alcoholism was also more common than in previous studies, apart from the San Diego Suicide Study. The study emphasised the impact of comorbidity in mental disorders in completed suicides (Henriksson et al 1993). However, the sex differences in the various patterns of substance use disorders and their comorbidity in completed suicide remain largely unknown.

4.2.2. Role of life events in completed suicide

Clinical studies of suicides have found psychosocial stressors in most suicide cases, with interpersonal losses and conflicts, medical illness and economic problems being the most common (Ripley & Dorpat 1981, Rich et al 1991, Murphy 1992, Marttunen et al 1993, Duberstein et al 1993, Heikkinen 1994). A strong relationship between such stressors and alcohol dependence, and a greater frequency of interpersonal loss in alcoholics compared to depressives in the six weeks prior to their death, have been repeatedly reported in psychological autopsy studies (Murphy & Robins 1967, Duberstein et al 1993, Heikkinen 1994). In addition to clustering of adverse events prior to suicide, a set of cumulative risk factors for alcoholic suicides has been presented, including current heavy drinking, major depressive disorder, lack of social support, unemployment, serious medical illness, living alone and suicidal communication (Murphy et al 1992).

4.2.3. Treatment of substance dependent suicide victims

Despite numerous psychological autopsy studies of completed suicides (Table 3) little is known about the help seeking by substance dependent victims and the treatment they receive, although a few studies have reported psychiatric hospitalisations, multiple admissions and general medical contacts among alcohol dependent victims (Barraclough et al 1974, Runeson 1990, Murphy, 1992).

4.2.4. Alcohol intoxication at the time of suicide

With regard to the final act of suicide, alcohol as an intoxicating substance has been suggested to impair judgement, cause impulsivity and contribute to the choice of suicide method (Welte et al 1988, Hayward et al 1992, Öhberg et al 1996). Current substance abuse is a known risk factor for suicide among victims with a substance use disorder (Murphy et al 1992, Bukstein et al 1993). Hayward et al (1992) found alcohol in the blood in 35.8% of 515 Australian suicides. Based on an analysis of victims in the National Suicide Prevention Project in Finland, Öhberg and colleagues (1996) reported alcohol in the blood in 40.9% of male and 19.6% of female suicides. However, the contribution of an inebriated state to the final act of suicide is not yet well understood.

4.3. Alcohol and variation in suicide rates

4.3.1. Alcohol consumption and suicide rates

Suicide rates are associated with levels of alcohol consumption and heavy drinking in populations (Smart & Mann 1990, Gruenewald et al 1995, Mäkelä 1996, Caces and Harford 1998). Mäkelä (1996) reported that in male age groups 15-34 and 35-49 years the suicide rate in Finland from 1950 to 1991 was associated with per capita alcohol consumption. A similar effect was found in the United States when unemployment was statistically controlled for (Caces and Harford 1998), and a decline in suicide rates in former USSR countries has was reported following strict restrictions on alcohol sales (Wassermann et al 1994).

4.3.2. Temporal variation in suicide rates

Temporal variations in suicide frequencies have been reported (MacMahon 1983). There is evidence that rates vary according to season (Kevan 1980), and a peak of suicides on Mondays has been found (Chew et al 1994, Lester 1979, Schmidtke 1994). A lower incidence at the weekend has been observed, and the peak incidence of the first days of the week has been explained in terms of a transitional phase between the extreme situations of weekend and workdays (Massin et al 1985). In alcohol-associated deaths alcohol has been detected more commonly in persons who died on weekend days, and in suicides with alcohol in the blood there was a slight increase associated with weekends (Smith et al 1989). Temporal variation in heavy alcohol use may explain part of the monthly variation in suicide rates (Poikolainen 1982).

Another factor related to the temporal variation in suicide rates is unemployment (Pritchard 1992). In general, unemployment results, via the financial strain, in negative health effects and leaves the individual more vulnerable to the impact of unrelated adverse life events (Kessler et al 1987). Those exposed to unemployment reportedly have more mental disorders, substance use and suicidal behaviour than those not exposed (Fergusson et al 1997). Moreover, employment is associated with lower rates of psychiatric disorders (Bebbington et al 1981). There seem to be epidemiological associations between unemployment and both suicidal behaviour (Platt 1984) and completed suicide (Pritchard 1992, Lewis & Sloggett 1998).

4.4. Substance use disorders and suicide prevention

It has been suggested that a comprehensive general strategy for the prevention of suicide behaviour should consist of research, improving services, training and information on suicide, and focusing on special groups (Diekstra 1992). On the basis of existing findings, identification and adequate treatment of major psychiatric disorders in health care, and interventions for deliberate self-harm patients may be effective measures for baseline suicide prevention (Hawton 1994, Rihmer 1996, Lewis et al 1997). A challenge in clinical work is to identify subjects at risk for suicide or suicide attempts. Recently, on the basis of research on suicide attempts, a clinical multifactorial diathesis model for assessing suicidal risk among psychiatric patients was proposed, in which in addition to psychiatric illness including substance abuse, a history of impulsivity and aggressivity, and subjective experiences of hopelessness were emphasised (Mann et al 1999).

There is reason to believe that primary prevention in terms of reducing general alcohol consumption would have some decreasing effect on suicide rates, possibly by moderating alcohol use problems (Mäkelä 1996). As alcohol consumption and suicide rates seem temporally related, there may be a time-related variation in the size of a population of individuals with alcohol misuse contributing to their suicide risk.

The ultimate aim of studies of completed suicides is to discover specific information for use in prevention, in terms of identifying subjects at risk and reliably recognising preventable risk factors. With regard to studying substance use disorders and suicide, information is needed about the sex- and age-specific characteristics of substance dependent subjects who eventually commit suicide, the factors associated specifically with their suicides, and their treatment contacts before suicide, if any exist. Evidence of any direct contribution of alcohol inebriation during the final act of suicide would also be important.