Suicides in LOS Angeles County in relation to the Northridge earthquake

Recently, there has been speculation that suicide rates increase after a disaster. Yet, in spite of anecdotal reports, it is difficult to demonstrate a systematic relationship between suicide and disaster. Suicides are fairly rare events, and single disasters rarely have covered geographic areas with large enough populations to be able to find statistically significant differences in such relatively rare events (annual suicide rates in the United States average 12/100,000 population).

Suicide rates increased in the three calendar years (1994-1996) following the Northridge earthquake as compared to the three calendar years (1991-1993) prior to the earthquake. Likewise the suicide rates for 1993 are compared with the rates in 1994. By looking at the suicide rates in a three-year period after the earthquake, the additional disasters that befell Southern California in 1995 and 1996 may have had an additive effect on psychological disorders and suicide rates that can be measured.

Data on suicide mortality were compiled for the years from 1989 through 1996. Differences in rates for 1993 compared with 1994 and for three-year periods before and after the earthquake (1991-1993 vs. 1994 -1996) were analyzed using a z-statistic.

There is a statistically significant difference in the rates for the years prior to the earthquake (1991-1993) when pooled and compared to the suicide rates for the years after the earthquake (1994-1996). The rates of suicide are lower in the three years following the earthquake (11.85 vs. 13.12/100,000 population) than they are in the three years prior to the earthquake (z = -3.85, p < 0.05). Likewise, there is a similar difference when comparing 1993 to 1994 (11.77 vs. 13.84, z = -3.57, p < 0.05). The patterns of suicide remain similar over time, with males and non-Hispanic Whites having the highest rates of suicide.

It does not appear that suicide rates increase as a result of earthquakes in this setting. This study demonstrates that the psychological impacts of the Northridge earthquake did not culminate in an increase in the rates of suicide.