Joint heavy use of alcohol, cigarettes and coffee and the risk of suicide

Aims. To estimate the relationship between joint heavy use of alcohol, ciga rettes and coffee, and the risk of suicide in a general population with hig h rate of suicide. Design. Prospective cohort analyses. Setting. Finland. P articipants. Data from 36 689 adult (age range 25-64 years) men and women w ho participated in the population surveys between 1972 and 1992. Measuremen ts. The mortality of the cohort was monitored for a mean of 14.4 years, whi ch yielded 169 suicides. Criteria for heavy use of each psychoactive substa nce were defined as follows: alcohol (>120 g/week), cigarettes ( greater th an or equal to 21/day) and coffee (greater than or equal to seven cups/day) . Findings. About half the men and 80% of the women did not use any of the psychoactive substances heavily. Every third man and every fifth woman used one substance heavily, and the prevalence for those who exceeded criteria for joint heavy use of two substances was 9% for men and 1% for women. Join t heavy use of all three substances was rare. The adjusted relative risk of suicide increased linearly with increasing level of joint heavy use of alc ohol, cigarettes and coffee. Among subjects with heavy use of one substance the risk was 1.55 (95% CI = 1.10, 2.18), with joint heavy use of two subst ances 2.22 (95% CI = 1.37, 3.61), and with joint heavy use of all three sub stances 3.99 (95% CI = 1.80, 8.84) compared with no heavy use. Conclusions. Clustering of the heavy use of alcohol, cigarettes and coffee could serve as a new marker for increased risk of suicide.