Suicide and Homicide Rates

Suicide and Homicide Rates

Note: this is part of the Youth Suicide Rise project.

Is there a link between violence and suicide?

Let us first ask a more precise question: is there a correlation between suicide and homicide among youth?

Male Youth

Let us first look at males (age 15-19):

While there might be a correlation, it is not a very robust one, as there are long periods -- such as 2007 to 2014 -- when homicide and suicide trends were opposite.

If we turn to linear correlation, we do find some evidence of a link:

It is clear from the graphs, however, that this moderate correlation would largely disappear if we remove the 7 or so years in the 1990's period of high homicide and suicide (1992-1996).

Female Youth

The correlation between homicide and suicide among female youth is minuscule and negative:

Homicide and Gender

It is important to keep in mind here that females get killed primarily by males (typically in a domestic setting), so rising violence against women need not imply similarly rising violent conduct among these women.

Among males the situation is different: the vast majority of males are killed by other males, often outside their home; furthermore youth males tend to be killed by peers.  Therefore homicide rates among male youth are presumably a very good indicator of violent conduct among male youth.

Female teens are also much less likely to be victims of a homicide than male teens: their chances of being killed are nearly one third those of male teens.

Discussion

None of the above results exclude the possibility of a significant link between male homicide and suicide; it could simply be that its moderate strength gets overpowered by stronger trends.  For example, decreasing homicide rates might slower a rising suicide trend.

The fact that there is no correlation among females but there is a moderate correlation among males suggests that there is indeed some link, perhaps due to underlying factors (e.g. aggressiveness and impulsiveness).

We will next look at the relationship between homicide rates and the male/female suicide ratio.

Note: I do not go into statistical details such as p-values because we are at this point merely investigating plausibility; once I transfer data into the statistical language R environment, I will revisit topics like these in more statistical depth.