A number of studies have indicated that when lethal means are made less available or less deadly, suicide rates by that method decline, and frequently suicide rates overall decline. This has been demonstrated in a number of areas: bridge barriers, detoxification of domestic gas, pesticides, medication packaging, and others.
For example, in rural areas of Asia and the Pacific Islands, pesticides are a leading method of suicide attempt (Gunnell 2003). Pesticides in widespread use have changed over time, and suicide deaths have been observed to rise and fall with the toxicity and case fatality rate of the particular pesticides currently in use. For example, the suicide rate in Samoa rose and fell with the introduction and control of paraquat, a pesticide that was more lethal than the pesticides in previous use in the country. Suicides declined dramatically in Sri Lanka following restriction of more lethal pesticides (Gunnell 2007).
Coal Gas in the United Kingdom
Prior to the 1950s, domestic gas in the United Kingdom was derived from coal and contained about 10-20% carbon monoxide (CO). Poisoning by gas inhalation was the leading means of suicide in the UK. In 1958, natural gas, virtually free of carbon monoxide, was introduced into the UK. By 1971, 69% of gas used was natural gas. Over time, as the carbon monoxide in gas decreased, suicides also decreased (Kreitman 1976). Suicides by carbon monoxide decreased dramatically, while suicides by other methods increased a small amount, resulting in a net decrease in overall suicides, particularly among females.
Over time, rates of suicide began to increase again although not to the pre-1965 levels. One author has estimated that over a ten-year period, an estimated six to seven thousand lives were saved by the change in domestic gas content (Hawton 2002)
Reducing access to lethal means does not always reduce the overall suicide rate. For example, restricting a low-lethality method or a method infrequently used may not make a detectable difference in the suicide rate. Restricting a very low-lethality method-if it results in attempters substituting a higher-lethality method-could in fact increase the overall suicide rate. Means reduction doesn’t change the underlying suicidal impulse or necessarily reduce attempts: rather, it saves lives by reducing the lethality of attempts
- When Do Means Matter? a worksheet that examines when means reduction is likely and unlikely to result in an overall decline in suicides.
- More studies involving bridge barriers, pesticides, medications, and other methods.
Gunnell D and Eddleston M. Suicide by intentional ingestion of pesticides: a continuing tragedy in developing countries. International Journal of Epidemiology. 2003;32:902-909.
Gunnell D, Fernando R, Hewagama M, Priyangika WD, Konradsen F, Eddleston M. The impact of pesticide regulations on suicide in Sri Lanka. Int J Epidemiol. 2007;36(6):1235-42.
Kreitman N. The coal gas story. United Kingdom suicide rates, 1960-71. Br J Prev Soc Med. 1976 Jun;30(2):86-93.
Hawton K. United Kingdom legislation on pack sizes of analgesics: background, rationale, and effects on suicide and deliberate self-harm. Suicide and Life-Threatening Behavior. 2002;32(3):223-229.