Does natural family planning decrease divorce rates?

Question

According to Dr. Janet Smith's lecture "Contraception Why Not" the Family of the Americas Foundation performed a study regarding rates of divorce and the use of Natural Family Planning techniques (as opposed to oral contraception, sterilization, etc...).

The statistic of 5% divorce rate for couples using NFP is what I commonly hear and read.

Perhaps this is why divorce rates for NFP users are between 1/10 and 1/25 of the overall divorce rate in the United States in the 90s.4 Indeed, a study conducted by the Family of Americas Foundation found only 16 women ever divorced among 505 NFP users, a rate of 3.6%!5

Link to the study: [http://familiadelasamericas.org/inc/data/divorce_study_eng_wilson.pdf]

According to the text of the study, this is the first study of it's kind. Was it so conclusive that it was also the last study of its kind? Does Natural Family Planning really dramatically reduce the chance of a couple to get divorced?

Here's what the USCCB (United States Council of Catholic Bishops says the correct way to do the study would be:

if a researcher wanted to determine whether there is a difference in divorce rates among married couples who use NFP versus couples who use oral contraception, the study would be designed to track first time NFP and first time oral contraception users over a 10 to 20 year period. But what if a researcher did not have the time or money to track couples over a long period of time but still wanted to investigate the same issue? A "cross sectional" longitudinal study could be conducted instead. To do this study a large sample of married couples from NFP centers that have records from the 1970s and early 1980s would be needed. Next, a comparison of that data with a large sample of married couples who attended family planning clinics to obtain oral contraception in the same time period would have to be done. Once large enough samples are obtained from each grouping, an interview (by phone, in person or through mail) of the participants would have to be conducted in order to determine which of the couples divorced and the frequency of doing so.

Is that sufficient, does the Family of the Americas Foundation even come close?

Divorce rates among Catholics (who make up the majority of the study) have been shown to be similar to other sects. An easy assumption is that this study just proves that faithful Catholics are far less likely to wind up divorced, but that should have no bearing on the question. But if correlation doesn't imply causation, does that assumption even have any merit?

Answer 1

Looks like I was beaten to the punch, but there are a lot of issues here.

1. First, as Kibbee said in the comments, this is a whole lot of correlation, not necessarily causation. That should be enough.
2. This is also, to put it delicately, a very biased study (if you want to even call it a study). Right off the bat, just from the name of the organization, you can see that they obviously had a goal in mind when publishing this. From that alone, I'm not at all convinced that they're not skewing data towards their goals as much as possible. But that position is further reinforced in the very first paragraph (emphasis mine):

   Authentic Natural Family Planning never interferes with the transmission of life; its sincere openness to the Will of God and respect for life is its most vital virtue. Various natural methods are being taught throughout the world that respect the natural law and are accepted by most cultures and religions.

3. On the third page, we start to see unfounded, personal opinion (emphasis mine):

   In contrast, couples who use artificial methods of birth control seem to experience disturbing spiritual, and psychological as well as physical risks to their body and soul.

   We see more of this on the fourth page as well (emphasis and footnotes mine):

   Artificial methods do not encourage intimate communication between spouses as they transfer the burden of responsibility primarily on the woman¹. Artificial birth control places an artificial barrier between husband and wife and limits the most intense physical expression of human love. Such methods facilitate the couple’s use and misuse of each other rendering them unable to fully appreciate the gift of their sexuality.

   ^{1: Really? I mean, I have no data to back this, but it sure seems like male condoms are probably the most prevalent form of birth control worldwide...}

4. But then, also on page four, the actual scientific problems with the study/survey start. They freely admit that this is a non-random, non-representative study of the general population in America (emphasis and footnotes mine):

   505 women returned useable completed questionnaires to an independent investigator retained by Family of the Americas Foundation to provide data entry and descriptive statistical analysis. The survey achieved a 74% response rate. Sampling for the NFP study was nonrandom, although the investigator did attempt to generate a representative sample of women in the U.S. who practice NFP.¹

   ^{1: Impossible, since they're intentionally only drawing from their pool of active participants.}

5. The last straw for me before I stopped reading was on page five, when they give the demographics of the women involved (emphasis mine):

   The NFP respondents had taken instruction in Natural Family Planning at least three to over ten years ago. 92% of the women were White, 6% Hispanic and the remaining 2% Other.

There are just so many things wrong here, that any result they come up with should not be taken at all seriously. They've got an agenda, they most likely had a hypothesis they were out to prove, they're introducing opinion into what should at least try to be a scientific paper, they're not sampling randomly, they're only taking from their own participant pool, and the participant pool itself was demographically skewed.

Did they look at age? Income? The number of years a couple had been together/had been married? If the couple had lived together before getting married? If they had already had kids or not before getting married? If they had already had kids or not before getting divorced? If so, how many? This is all just off the top of my head.

So no, I sincerely doubt Natural Family Planning dramatically reduces the chance of a divorce.

Edit: Responding to the modified parts of your question. I wasn't sure what the USCCB was, but Googling it led me to the United States Conference of Catholic Bishops, so I'm assuming that's what you're referring to. The quote you've posted (seeing where you got it from would be nice) is a much better track to take, but as has been said, FAF isn't really approaching that at all. Think about all the questions I asked at the end of my original answer, and whether they (and others) are being addressed.

As far as the assumption you make that the study proves that faithful Catholics are less likely to be divorced... well... that's really quite an assumption. What defines a Catholic as faithful? That the Church condemns divorce and so they'd never do it? Were all the people in FAF's study part of that group? Is that really "faith"? I could just as easily assume that all the study proves is that white people are far less likely to wind up divorced. When you get into subjective land, it's tough to get out. So no, that assumption really doesn't have much merit either.

Answer 2

Ok, class, say it with me. Correlation does not imply causation. There could be many confounding factors that explain the correlation.

In my original draft of this answer, I tried to show that religiosity is one such confounding factor. I showed that contraceptive use is inversely correlated with religiosity (Source). But when I went to show divorce rates were also inversely correlated to religiosity, I found that wasn't true - not even in the religious groups that eschew contraception! (Source)

So, you will just have to come up with your own ideas for confounding factors...

Answer 3

The study referenced is fundamentally flawed. The correct way to do a study like this is to make a random sample of people, and get some to practice NFP and some to practice other methods. Then compare the results. Failing that it is possible to conduct a study based on non-random samples, provided you make sure both samples are representative of the general population.

This study doesn't come close to that. It's based on a survey of people who were trained, and practice, NFP. And unsurprisingly, according to the study 91% of the people practicing NFP gave their religion as Roman Catholic. It's not surprising because the Roman Catholic church is one of very few organizations recommending NFP as a means of contraception.

Well, the Roman Catholic church also forbids divorce. So it is completely unsurprising that the people in the survey also have a very low divorce rate, compared with the general population. But it isn't NFP that's causing it - it's the fact that Active Roman Catholics have both a much higher rate of NFP use and lower divorce (23%). It's correlation, but not causation. The comments made by Dr Smith are entirely bogus.

(It's true that Catholics in general have only a slightly lower divorce rate than the general population, but non-active Catholics are unlikely to be practicing NFP)

So to summarize, the survey is of a self-selecting sample that has a high NFP use rate and also is almost guaranteed to have a much lower divorce rate than the general popuation.