Well, the good professor was kind enough to reply--it would seem the 80% statistic is a bit of a myth. Interesting how these things get repeated so often they end up becoming truths--the factoid just got cited in Town and Country magazine:

I would be quite skeptical of such a statistic. As you know, some years ago I worked on the topic and found a modest increase in the risk of divorce with a disabled child. A rate of 80%, however, is very much higher than the average risk of divorce. I have not followed the literature, but I just went onto Google Scholar (scholar.google.coM) and find nothing directly relevant except for my paper. That’s not very surprising to me because actually, even measuring divorce rates is not a straightforward matter (it requires observing couples multiple times over a relatively long period), and measuring the impact of any factor on divorce rates is not easy. A factor such as “childhood disability” is also complex and not easily measured. My own efforts were very crude.



My overall comments are these:

Clearly, having a disabled child is a very stressful experience -- there is a considerable literature on the very high levels of stress experienced by parents. Stress, as well as the time demands of raising a disabled child, can certainly impair the quality of the marital relationship. How much the quality of the relationship is impaired varies from couple to couple, as do their capacities (emotional, practical, financial) to engage in relationship “repair work” to help sustain the relationship. Sometimes the courage and persistence needed to deal with disability can foster new respect between partners.



Most couples need support and sometimes actual help in protecting or restoring the quality of their marriages, and parents of disabled kids may need more than most (and may get less than most). So marriage relationships may certainly be of “lower quality” on average among parents of disabled kids—though I’m on thin ice (lacking empirical backing) making even that suggestion.



Divorce is a specific option couples use to “deal with “ (or not deal with) a poor-quality relationship, but it is certainly not the only possible option. Having a disabled child may, in fact, make the option less available, for reasons of money, obligation, loyalty or concern for the child. Equally, it may make the option more appealing. But I don’t know of any statistics on how these competing pressures actually play out.