The Association Between Alcohol Consumption and Suicide Rate for Different Employment Levels
1. Introduction
Alcoholic beverages have been drunk by people around the world since ancient time for different reasons, such as the relaxant and euphoric effect of alcohol. Alcohol consumption is widespread in almost all countries for recreational purpose due to its popularity during social occasions.
Although alcoholic beverages are drunk in almost all countries, consumption varies a lot from country to country, not only because of different laws and restriction, but also because of social and religious implications.
However, the excessive consumption of alcohol can be harmful for the human and can lead to temporary or permanent alcohol-related impairment in some area of life as a result of drinking.
Some studies show how the excessive use of alcohol consumption seems to be associated with a more impulsive and aggressive behaviour, due to serotonin depletion (1).
Impulsive and aggressive behaviour are also typical features implicated in suicidal behaviour.
Those countries where alcohol consumption is higher (possibly due to the misuse of alcohol by some part of the population) seem to experience higher level of suicide rate amongst their population.
This might be due to the fact that countries with higher level of alcohol consumption include individuals more prone to alcohol abuse as they are also experiencing difficult situations in life.
Other factors might come into play when looking at the association between alcohol consumption and suicide. One potential factor that might be correlated with hardship in life is unemployment or low level of employment rate.
For this reason, it might be interesting to observe through this research study the nature of association between alcohol consumption rate and suicide rate for different levels of employment amongst the different countries.
1a. Research Questions
Is alcohol consumption associated with suicide rate?
Is the association between alcohol consumption and suicide rate different for countries with different level of employment?
2. Methodology
For the purpose of our analysis, we examined the data set provided by the Gapminder non-profit venture.
2a. Sample
Gapminder collected data for the 192 UN members, aggregating data for Serbia and Montenegro. Additionally, it included data for other 25 areas, generating a total of 215 areas.
Gapminder has collected data from a handful of sources which includes Health Metrics and Evaluation, US Census Bureau’s International Database, United Nations Statistics Division, and the World Bank.
However, for this project, we subset the data set in order to eliminate those observations where suicide rate, alcohol consumption and employment rate were left blank (or N/A). Our final sample included data from 166 countries.
2b. Measures
Alcohol consumption data were collected by the WHO in 2008. It was recorded and estimated as average consumption per adult (age 15+) and measured as per capita consumption of pure alcohol in litres.
Suicide rate (recorded as suicideper100th) data were collected by the WHO Violence and Injury Prevention (VIP) and WHO Global Burden of Disease in 2002 and 2004. It was measured as mortality due to self-inflicted injury, as per 100,000 standard population.
Employment rate was collected in 2007 by the International Labour Organisation, and recorded as the percentage of total population, age above 15, that has been employed during the given year.
3. Results
3a. Univariate
On average, alcohol consumption amongst the 166 countries in our sample set was 6.65 (litres of pure alcohol per capita), with a standard deviation (s.d.) of 5.034. Alcohol consumption distribution was positively skewed, with the majority of the data lying in the lower ranges, and fewer observations in the medium-high ranges.
Similarly, suicide rate was positively skewed, with a mean of 9.97 (suicides every 100,000 people) and a standard deviation of 6.48.
Employment rate was normally distributed, with a mean of 59.23 (percentage of population employed) and a standard deviation of 10.34.
3b. Bivariate
Pearson correlation test confirmed our initial assumption: that is, alcohol consumption (quantitative explanatory) and suicide rate (quantitative response) are positively and significantly associated (r = 0.37; p<.0001). However the r coefficient (0.37, with a maximum value of 1) indicated that the nature of the association is not exceptionally strong.
Analysis of variance (ANOVA) and post-hoc Duncan test revealed that the means of suicide rate for each alcohol consumption level (this time considered as a categorical variable, for which 6 different buckets were created) are significantly different only for the highest level of alcohol consumption vs. other levels (level 6, consumption higher than 15 litres per capita, group A in the chart below). The means of the other groups (1-5) are not significantly different amongst each others (group B).
Further ANOVA between alcohol consumption (considered as quantitative response variable) and employment rate (categorical explanatory variable) revealed an association between the two variables (F= 5.27; p <.0017). The difference of alcohol consumption means differs significantly amongst the various employment rate buckets. In particular, the 2nd and 3rd quartiles of employment rate have higher alcohol consumption means than the 1st or the 4th. Alcohol consumption is higher in the medium-low and medium-high level of employment (possibly connected to purchasing power as well), whilst is lower for the lowest and the highest levels of employment.
The third variable employment rate moderate the association between the explanatory variable alcohol consumption and suicide rate. For low-medium level of employment rate (quantile 1 and 2) the association between alcohol consumption and suicide rate is stronger and significant (1st quantile, r = 0.50, p < 0.0009, 2nd quantile: r = 0.48, p < 0.0013). For higher level of employment rate, the association is much weaker and not significant. See the chart below.
4. Discussion
4a. What the results might mean?
Alcohol consumption and suicide rate are positively and significantly associated. This confirms the original assumption; i.e. that higher alcohol consumption - that can lead to impulsive and aggressive behaviour when the person is intoxicated - is implicated in suicidal behaviour. Although the relationship is not strong, countries with higher alcohol consumption per capita tend to have higher suicide rates. Some studies confirm that intoxicated people are more likely to attempt suicide using more lethal methods (2). Employment rate, although not significantly associated with suicide rate, affects the direction and the strength of the association between the dependent and the independent variable. For lower levels of the employment rate, countries with higher level of alcohol consumption per capita are more likely to have higher suicide rates. For countries with high level of employment, the association is much weaker and not statistically significant; i.e. high alcohol consumption per capita doesn’t necessarily correspond with high suicide rates. 21 of the top 30 positions for suicide rate are occupied by countries with higher than average alcohol consumption per capita; 20 of these have also low-medium employment rate. Interestingly enough, more than a third of the countries with the highest suicide rate used to be part or under the USSR sphere of influence during the cold war period (in order: Lithuania, Russia, Belarus, Kazakhstan, Latvia, Hungary, Slovenia, Ukraine, Estonia, Moldova and Croatia). This observation suggest potential further researches.
4b. Strengths
Results are based on data collected for 192 countries and 25 areas (166 countries after eliminating countries with incomplete results). According to Gapminder, the data collected is the most current for each country. 4b. Limitations
The data gathered by Gampminder were collected over different years so association between different variables might be hindered by this fact. In particular, data for suicide rates and alcohol consumption were collected 4 years apart. Over this period, some trends might have changed. Another limitation concerning the employment rate is that this is not necessarily an accurate indicator of the well-being of a country, as in some under-developed countries, younger people might be forced to quit education to enter the unskilled workforce. 4c. Recommended Future Researches
Certainly there are some other variables that influence the association between alcohol consumption and suicide rate. Our initial hypothesis was that hardship in life can be a contributing factor in linking alcohol and suicide. Low employment rate seems to strengthen this relationship; however other factors might come into play in regulating the association, such as rates of major depression, alcohol dependance (not just consumption), weapons per capita, religious and social code. Also, the fact that a bunch of countries with high alcohol consumption and suicide rate used to belong to the USSR sphere of influence block suggests that a particular social environment in which people grew up in might be another relevant factor when evaluating the association between alcohol consumption and suicide rate. The presence of some Baltic and Scandinavian countries at the top of the list might suggest to investigate the latitude and climate relationship with alcohol and suicide. Furthermore, the competitiveness of the social environment (2) can be another factor influencing the association investigated today; the presence of Japan and South Korea high up in the list suggest further research on this factor.
5. References
(1) Lowinger D., The role of Serotonin in Alcohol's effect on the brain, http://www.currentseparations.com/issues/18-1/cs18-1d.pdf
(2) Sher L. , Alcohol consumption and suicide, Oxford Journal, http://qjmed.oxfordjournals.org/content/99/1/57.full
(3) Stressed and depressed, Koreans avoid therapy, New York Street Journal, July 2011, http://www.nytimes.com/2011/07/07/world/asia/07iht-psych07.html
6. Appendix
SAS code
SAS Output