Cross-Sectional Studies of Gun Laws and Suicide

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