Cross-Sectional Studies of Gun Laws and Suicide
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We identified 14 cross-sectional studies of the association between strictness
of gun control laws and rates of suicide; these studies are summarized in
Table 7-4. Overall, most studies found that stricter gun laws were associated
with lower gun suicide rates. For example, 8 out of 9 studies found that states
or cities with stricter gun control laws have lower rates of gun suicide. These
studies have used a variety of methods for classifying the types and strictness
of gun laws; it is worth noting that many of them compare the same geographic
areas over the same time intervals, so they should not be regarded as
independent samples. In general, laws restricting the buying and selling of
firearms have been associated with lower rates of firearm suicide, but laws
governing the right to carry firearms seem to have no association.
Lower gun suicide rates have sometimes been associated with higher
nongun suicide rates, and the findings regarding overall suicide rates have
been less consistent: 5 out of 11 studies found an association between
stricter gun laws and overall rates of suicide, another 5 studies found no
significant association, and 1 study produced mixed results.
Time Series Studies of Gun Laws and Suicide
A number of studies have described the trends in gun suicides in one or
two local or national jurisdictions before and after the passage of a gun
control law. Studies using one or two jurisdictions are summarized in Table
7-5; most of these studies have also been reviewed in previous chapters.
These studies present conflicting findings about the association between
gun laws and suicide, depending on the model specification and time period
under study. For example, several reports by Rich et al. (1990), Carrington
and Moyer (1994), Leenaars and Lester (1999), and Lester (2000) reach
different conclusions about the trends in gun suicide and overall suicide and
homicide in Canada before and after the passage of restrictive gun control
laws in 1977, compared with trends in the United States over the same
period of time.
Another notable example in this literature is the study by Loftin et al.
(1991) evaluating the District of Columbia’s Firearms Control Regulations
Act of 1975. This study has been prominently cited as showing a significant
decline in gun suicides following the institution of a ban on handguns. However,
overall suicides, not gun suicides, are the policy question of interest, and
the investigators did not report whether there were significant differences in
the estimates of the trend in overall suicide rates. Other concerns about the
Loftin study were raised in Chapter 5 in relation to homicide, and they are
likely to apply to the results pertaining to suicide as well.
The overall problem with the interrupted time-series study design is that
simple comparisons cannot distinguish the effects of passage of a gun law from
the effects of a myriad of other factors that may be changing over the same
period of time. We identified four studies, summarized in Table 7-6, that
improve on this research design by using “difference-of-differences” methods
across many jurisdictions to evaluate the effect of gun policies on suicide rates.
These studies compare the differences in outcomes before and after the introduction
of a new policy in the various jurisdictions in which such policies have
been introduced, with the differences in the outcomes over the same period of
time among otherwise similar jurisdictions that have not been exposed to a
change in policy. By making comparisons within the same jurisdiction at multiple
points of time and across many jurisdictions at any single point in time,
investigators hope to control for unobserved characteristics of the jurisdiction
that do not change over time and for unobserved time trends that may be
shared across jurisdictions. As with the simpler interrupted time-series design,
the validity of the results depends on many assumptions about how and when
the law was implemented, how long it might take for the law to have a
discernible effect on the use of firearms, how long such an effect might last, and
about the presence or absence of other factors that might affect the suicide rate
during the time when the gun law came into effect.
TABLE 7-4 Cross-Sectional Studies of Gun Laws and Suicide
Units of
Source Analysis Gun Law
Kleck and 170 large 10 types of law,
Patterson cities, 1979- or aggregate index
(1993) 1981
Yang and 48 states, Strictness of state
Lester (1991) 1980 gun control laws
(update of
Sommers, 1984)
Boor and 50 states, Three types of
Bair (1990) DC gun laws
1985
Lester 9 regions, Strictness of
(1988c) 1970 handgun control
laws
Lester 48 states, Strictness of
(1987a) 1970 handgun control
laws
Lester and 48 states, Strictness of
Murrell 1960, 1970 handgun control
(1986) laws 1964-1970
Sommers Nine types of laws
(1984)
Medoff and 50 states, (a) type of law
Maggadino 1970 (b) strictness of
(1983) enforcement
DeZee (1983) States Individual and
1978 aggregated gun
laws
continued
Results Results: Results:
Gun Nongun Overall
Controls and Strata Suicide Suicide Suicide
% black, % male, median age, Index: Index: 0 Index: 0
unemployment rate, poverty, decrease
income, home ownership, college Permit: Permit: 0
enrollment, transience, population decrease Mental: 0 Mental: 0
change, divorce, church Mental: Dealer Dealer
membership, etc. decrease decrease decrease
Other: 0 Other 0
Gun ownership: various proxies Dealer:
decrease
Other: 0
Unemployment, divorce Decrease Increase Decrease
% male, % 35-64, % black, % n/a n/a Decrease
urban, population density; %
population change, divorce rate,
crime rate, unemployment rate
% black, median age, % urban, 0 0 0
divorce rate
Gun ownership: Wright survey
None Decrease 0 0
None Decrease “Other” Overall:
increase decrease
male:
decrease
female: 0
Divorce rate, unemployment rate Wait: n/a n/a
decrease
Mental:
decrease
White male suicide rates only: n/a n/a Decrease
age, median income,
unemployment rate, occupational
prestige, % catholic, region
% unemployed, % male, % n/a n/a 0
youth, % white collar, % blue
collar, % foreign born
TABLE 7-4 Continued
Units Of
Source Analysis Gun Law
Lester and 48 states Three types of
Murrell 1960, 1970 gun laws
(1982)
Lester and States, Strictness of gun
Murrell 1959-1971 laws in 1968
(1980) 1969-1971
Murray 50 states, Seven types of
(1975) 1969 gun laws, 1966
Geisel et al. 50 states; Weighted index,
(1969) large cities, handgun laws
1960,
1965
NOTE: Decrease/increase: gun law predicts fewer/more suicides; 0 = effect not significant at p
=.05; n/a = not stated in report.
TABLE 7-5 Interrupted-Time-Series Studies of Gun Laws and Suicide
Time
Periods
Source Areas Compared Compared Gun Law
Lester (2000) Canada 1970-1996 1978
Bill C-51
Carrington Canada 1969-1976; 1978
(1999) 1978-1985 Bill C-51
Leenaars and Lester Canada 1969-1976; 1978
(1999) 1978-1985 Bill C-51
Cantor and Slater Queensland 1990-1991; 1992
(1995) (Australia) 1992-1993 Weapons Act
Carrington and Moyer Ontario 1965-1977 1978
(1994) 1979-1989 Bill C-51
Lester and Leenaars Canada 1969-1976; 1978
(1993) 1978-1985 Bill C-51
continued
Results Results: Results:
Gun Nongun Overall
Controls and Strata Suicide Suicide Suicide
None Seller: n/a
decrease increase
Buyer: Buyer:
decrease increase
Carry: 0 Carry: 0
None n/a n/a Decrease
% unemployed, median education, n/a n/a 0
% interstate migrants, % college
grads, % white collar, median
income, % foreign born, % young
adult, log of population
Per capita income, median Decrease n/a 0
education, % male, police per
capita, % nonwhite, population
density, licensed hunters
Change in Change in Change in
Gun Suicide Nongun Suicide Overall Suicide
After Gun Law After Gun Law After Gun Law
Decrease Increase Increase
Trend No change in Trend
flattens for trend for males flattens for
males males
Trend varies Trend varies by Trend varies
by age, sex age, sex by age, sex
Trend varies by Trend varies by Trend varies by
urban/rural, sex urban/rural, sex urban/rural, sex
Not Trend Trend
significant downward downward
Decrease Not significant
Not significant
In the first quasi-experimental study to examine effects of gun policy on
adult suicide, Ludwig and Cook (2000) evaluated the impact of the 1994
Brady act in 32 “treatment” states that were directly affected by the act,
compared with 19 “control” jurisdictions that had equivalent legislation
already in place. The authors found a reduction in firearm suicides among
persons age 55 and older of 0.92 per 100,000 (with a 95 percent confidence
interval = –1.43 to –.042), representing about a 6 percent decline in firearm
suicide in this age group. This decrease, however, was accompanied by an
offsetting increase in nongun suicide, so that the net effect on overall suicide
rates was not significant (–.54 per 100,000; with a 95 percent confidence
interval = –1.27 to 0.19). Using a similar methodology, Reuter and Mouzos
(2003) found no significant effect study of a large scale Australian gun buyback
program on total suicide rates.
TABLE 7-5 Continued
Time
Periods
Source Areas Compared Compared Gun Law
Snowdon and Harris Australian states 1968-1979; 1980 gun
(1992) 1980-1989 law
(South
Australia)
Thomsen and Denmark 1984-1985; 1986 law
Albrektsen (1991) 1986-1987
Loftin et al. DC vs. suburbs 1968-1976; 1976
(1991) (a) mean monthly 1977-1987 handgun
rates (b) ARIMA ban in DC
with age-standardized
annual rates
Rich et al. Toronto 1973-1977; 1978
(1990) 1979-1983 Bill C-51
Nicholson and Garner DC vs. nation Two 1976
(1980) selected handgun
years ban in DC
(1976;
1979)
NOTE: ARIMA = autoregressive, integrated, moving-average time series models.
Two other studies have evaluated the effects of safe storage laws on
child and adolescent suicide (see Chapter 8). Cummings et al. (1997a)
evaluated the possible effect of state safe storage gun laws on child mortality
due to firearms; they found an insignificant decline in gun suicides (rate
ratio 0.81, with a 95 percent confidence interval = 0.66-1.01) and overall
suicides (rate ratio 0.95, with a 95 percent confidence interval = 0.75-1.20)
for children under age 15 in states that had instituted such a law. In a
similar study, Lott and Whitley (2000) investigated the effects of safe storage
laws introduced in various states between 1979 and 1996. They compared
gun and nongun suicides among children in the age group most likely
to be affected by the law, as well as gun suicides in the next older age group,
which should have been unaffected by the law. Their models also controlled
for state and year fixed effects and 36 other demographic variables. They,
too, found some reduction in gun suicides among children in states with
stricter gun storage laws, but no reduction of overall suicide rates.
Change in Change in Change in
Gun Suicide Nongun Suicide Overall Suicide
After Gun Law After Gun Law After Gun Law
Decrease Increase No difference
(SA males) (S.A. males)
No change Not stated Decrease
(not qualified)
(a) Decrease (a) Not significant (a) Decrease
(not quantified)
(b) Not (b) Not stated (b) Not stated
significant
Decrease Increase-jumping Not significant
Decrease Not significant Decrease