God designed sexual expression to unite a man and woman in an intimately loving embrace that is total, faithful, free and fruitful—and thus in marriage. Indeed, the marital act is the beautiful, God-given expression whereby a man and woman become “one flesh” in marriage for the first time (Gen. 2:24), and wherein they thereafter renew their marriage covenant.
Consequently, masturbation is a sin against the Sixth Commandment, because it violates the God-inscribed unbreakable bond between the love-giving and life-giving aspects of the marital act (see CCC 2366-70). Instead of the intimate and mutual self-giving that is the hallmark of the marital act, masturbation—and whether within marriage or outside of marriage—is an act in which one turns selfishly inward.
Indeed, masturbation is a dualistic, self-indulgent activity that uses the body as a means of personal gratification, instead of integrating one’s gift of sexuality—one’s powers of love and life—into a sincere self-gift to another. Masturbation attempts to dualistically divorce the physical behavior we choose to engage in from shaping our self-identity, as if the former had nothing to do with the latter. Masturbation fails to see that our bodies are not something we have but are essential to who we are and how we express ourselves as human persons, as body-soul composites (CCC 364-65).
In his address to a group of U.S. Bishops in September 1983, St. Pope John Paul II counsels that eschewing dualism is indispensable to premarital and marital formation:
In order to avoid any trivialization or desecration of sexuality, we must teach that sexuality transcends the purely biological sphere and concerns the innermost being of the human person as such. Sexual love is truly human only if it is an integral part of the love by which a man and a woman commit themselves totally to one another until death. This self-giving is possible only in marriage. . . . This teaching must be the basis of all education in sexuality and chastity. It must be communicated to parents who have the primary responsibility for the education of their children, and also to pastors and religious teachers who collaborate with parents in the fulfillment of their responsibility.
Consequently, the Church has always definitively taught—and will always teach—that masturbation (CCC 2352) is “an intrinsically and gravely disordered action.” And when committed with full knowledge and complete consent (CCC 1859), it is a mortal sin (see CCC 1854-64).
So masturbation is certainly not essential for our health. To the contrary, especially regarding our moral well-being. In addition, God gives us his grace, particularly in the Sacrament of Reconciliation and Eucharist, to overcome our sinful sexual desires, as well as provides the support of the Church in general and also natural remedies, including nocturnal emissions for men.
For more on this subject, see the Church’s teaching on the distinction between mortal and venial sin (CCC 1854-64), chastity (CCC 2337ff.), lust and masturbation (CCC 2351-52), and purity of heart (CCC 2517ff.; see also 2514-16). In addition, see also our resources at the Catholic Answers website (Catholic.com).