The Introduction of Hormonal Contraception and the Incidence of Suicide Among Adolescent Girls

Objective:

Evaluate whether the introduction of hormonal contraception (HC) increased or decreased the risk of completed suicide among adolescent girls and women and, more generally, present evidence on the association between the diffusion of HC across Swedish markets and mortality by cause and age.

Importance:

HC is arguably the most important scientific advance of the last century. Regarded as a safe, effective, and affordable contraceptive method it is used by millions of women around the world. Yet, recent medical research has revealed a significant association between hormonal contraceptive use and subsequent depression and suicide; an effect most pronounced among adolescents. This study aims to estimate the effect of HC on suicide and mortality in a historical setting where contraceptive alternatives are limited and abortion is illegal.

Abstract:

This study aims to be the first to evaluate the short-run relationship between suicide and use of hormonal contraception (HC) proximate to the legalization of the pill. Recent medical research has pointed to an association between low dose HC use, depression, and suicide; an association most pronounced among adolescents (see Skovlund et al (2016), Skovlund et al (2018)). Yet, other epidemiological studies using have found a reduction in depressive symptoms associated with HC use (see Keyes (2013)). The relationship between HC use, mental health and suicide has been understudied both in population based epidemiological studies as well as the economic literature on the social and economic impact of technological innovations such as the pill. The lack of attention is particularly striking in the Swedish setting; within a decade of legalization over a quarter of the fecund female population was using high dose oral contraception on an annual basis, among these more than half of teenage girls.

Did the fertility control effects of the pill lead to a reduction in pregnancies and suicides among young women? This is a relevant question; autopsy data illustrates how pregnancy was common among Swedish women whom committed suicide (see Hedren (1901)). Although recent studies provide evidence of a plausible causal channel between HC diffusion and increased suicide, the total effect of this contraceptive innovation on suicide and mortality has not been studied. I combine Swedish market level data on HC sales with detailed individual data on cause of death for 2.5 million women born in Sweden from 1915-1964 to quantify the short-run impact of HC diffusion on female mortality, with a focus on suicide among adolescent girls.

The introduction of the pill is a natural experiment which allows for plausible comparisons of counterfactual suicide behavior in the absence of HC, an innovation relative to recent studies which rely on women whom never use HC as controls. I will compare changes in female mortality trends before and after the legalization of HC across geographic markets and age groups. Two types of empirical models are employed. A differences-in-differences-in-differences (DDD) design compares changes in mortality before-after the pill, among high-low pill use age groups, and high-low pill use markets, providing a descriptive analysis of the correlation between HC diffusion and suicide trends. This descriptive analysis will be supplemented by an instrumental variables (IV/OLS) model to provide causal evidence on HC use and suicide. Under certain assumptions the IV estimates provide an estimate of the causal effect of HC use on suicide behavior, absent the effects of omitted variables which may skew correlations between HC and suicide, hence providing a check on the DDD analysis and the importance of omitted factors.

OLS estimates use the actual diffusion of HC to estimate correlations between HC use and suicide behavior, while IV estimates will use predictions of HC use driven by measures from a century earlier to identify exogenous shifts in HC use and in turn the causal effects of HC on suicide and mortality. The choice of instruments relies on historical demographic and economic data, such as non-marital birth rates or wage and commodity prices from the 19th Century, to capture latent demand for HC unrelated to contemporaneous shocks. These pre-determined differences in latent demand are used to identify an exogenous source of variation in HC use.