Divorce's medical and psychological implications
Until recently it was thought that divorce was almost always a positive experience for spouses. More recent longtitudinal studies have revealed that many divorced people are no happier after divorce (although some are). For example University of Chicago sociologist Linda Waite [Waite 2003] analyzes the relationships between marriage, divorce and happiness using the National Survey of Family and Households. Her research shows that unhappily married adults who had divorced were no happier than those who had stayed married. The 13 measures of well being include self-esteem, personal mastery, depression, purpose in life and alcohol drinks per day.
Until recently it was also thought that children's difficulties with divorce, while common, were short-lived. However, recent work has shown that a major cost to children comes long after: when they attempt to form stable marriages themselves. There is extensive and heated debate over just how much harm, just how many children are harmed to what extent, what factors mediate the harm, and so on; however, even strong optimists such as Mavis Hetherington [Hetherington 2002] acknowledge that many (not all) children of divorce are substantially disadvantaged. However, Hetherington (a University of Virginia professor) also states that 70% of children coming from divorced families consider divorce an adequate answer to marital problems (even if children are present), compared to only 40% of children from non-divorced families. This suggests that divorce rebounds upon itself from one generation to the next. In addition, children from divorced families initiate sex earlier and are more likely to cohabit before marriage. Cohabitation before marriage is correlated with an 9% greater chance of getting a divorce [Bramlett 2001].
Children from divorced families have a higher chance of behavioral problems, are six times more likely to be abused (in their step families) than children in intact families, and have a greater chance of living in poverty [Fagan 2000]. Other social consequences of divorce are also known: "offspring of divorce were more likely to engage in criminal behavior, drug use, alcoholism and suicide than children of never-divorced children (A Divorce Free America p.4)."
Constance Ahron, who has published books suggesting there may be positive effects for children, interviewed ninety-eight divorced families' children for We're Still Family: What Grown Children Have to Say About Their Parents' Divorce [Ahron 2004]. Numerous subjects said things like "I saw some of the things my parents did and know not to do that in my marriage and see the way they treated each other and know not to do that to my spouse and my children. I know [the divorce] has made me more committed to my husband and my children." A primary claimed benefit of divorce for children is that they become more committed to avoiding divorce. However, children of divorce in fact divorce more often, so this putative effect provides no net benefit.
Ahron's method of asking adult children of divorce how they feel about it also has the well-known weakness of "self-report" studies. Researchers are unlikely to hear negative responses even from people who were harmed (people are unlikely to say "it destroyed me" or "I've never fully recovered" after years of adjusting to the fact of one's parents' divorce...).
In cases of extremely high conflict, divorce can be positive. An article in the Oklahoma Bar Journal [Bartlett 2004] defines "high conflict" in terms of ongoing litigation, anger and distress, verbal abuse, physical aggression or threats of physical aggression, difficulty in communicating about and cooperating in child care, or other court-determined factors. In marriages falling short of this standard, however, studies overwhelmingly find that divorce has serious costs for children's well-being.
In reviewing [Amato 1997], Norval D. Glenn and David Blankenhorn of the Los Angeles Times  comment that "Amato estimates that at most a third of divorces involving children are so distressed that the children are likely to benefit. The remainder, about 70%, involve low-conflict marriages that apparently harm children much less than do the realities of divorce..."
Medical statistics show that all parties to a divorce are likely (not certain) to suffer increased morbidity and mortality. See [Gallagher 1999] for additional statistics and references. For example, divorce:
* doubles the partners' risks of alcoholism and other substance abuse. Robert H. Coombs, Professor of Behavioral Sciences at UCLA, reviewed over 130 studies measuring how marital status affects personal well-being. They "attest that married people live longer and generally are more emotionally and physically healthy than the unmarried." Also, "studies consistently found more alcoholism and problem drinking among the unmarried than the married." The separated and divorced account for 70% of all chronic problem drinkers, and marrieds 15% [Coombs 1991].
* greatly increases the partners' and children's risks of depression. "Family disruption and low socioeconomic status in early childhood increase the long-term risk for major depression" [Gilman 2003].
* for men and women, leads to a several times higher rate of psychiatric care than married people. Studies vary, suggesting from 5 to 21 times the risk, and vary over whether men or women are more seriously affected [Marks 1998] and [Bloom 1979].
* multiplies men's suicide risk, making them nearly 9.7 times likelier than women to commit suicide even after controlling for other risk factors, according to a study by Augustine Kposowa, a University of California at Riverside sociologist [Kposowa 2003]. This study quantified earlier work [Kposowa 2000] that estimated an increased risk of 2.7 times for men. Divorce is now the leading factor linked with suicide.
* is the leading factor in child suicide and homicide rates [Lester 1993].
* reduces sons' life expectancy by about 4 years, daughters' by somewhat less, and parents' as well [for example, see [Smock 1993], [US Bureau of the Census 1991], [Dickson 1993], [Arendell 1995], [Amato 1991], and [Joung 1994].
* children of divorce are 5 times more likely to live in poverty (thus having poorer nutrition, health care, etc.) [McLanahan 1994].
Divorce also greatly increases the chances for
* stroke See [Engstrom 2004]: "Marital dissolution is followed by an increased incidence of stroke."
* cancer. Married cancer patients are also more likely to recover than divorced ones [Goodwin 1987].
* acute infectious diseases, parasitic diseases, respiratory illnesses, digestive illnesses, and severe injuries. See [Lawson 2000]. In support of these particular claims, that article cites [US Bureau of the Census 1991] and [Albrecht 1980].
* heart problems. Some research suggests that childhood trauma, including parental divorce, can lead to much greater risk of heart attack in later life. See [O'Rand 2005]. Combined with job stress, divorce led to a 69% increase of death rate among men with above average risk of heart disease [Reuters 2002].
* rheumatoid arthritis and osteoarthritis. [Mili 2002] shows a 30% increase in risk at any given age. [Kopec 2003] finds that parental divorce leads to increased risk of arthritis for children later in life.
* sexually transmitted diseases. For example, in Uganda "Results from a baseline survey of HIV-1 infection in the cohort of over 4,000 adults (over 12 years old) showed a twofold increase in risk of infection in divorced or separated persons when compared with those who are married." [Nabaitu 1994].
Many additional studies show health problems not only for children of divorce, but for children of single-parent families in general, or children of those single-parent families not caused by death of one parent. For example, the rate of Sudden Infant Death Syndrome was 3 times higher when the birth registery indicated both parents but they were unmarried, and 7 times higher when only the mother even appeared on the registry. [Office for National Statistics (UK) 2002].
Yale researcher Harold J. Morowitz [Morowitz 1975] comments that "being divorced and a nonsmoker is [only] slightly less dangerous than smoking a pack a day and staying married."
[Wallerstein 2000], which revealed some of these effects, was at first criticized because the subjects were all drawn from an affluent section of California rather than a broader sample. This is a real issue. However, more recent studies have confirmed her findings, and sometimes shown that her sample group was actually better off than average. Perhaps unsurprisingly, families with lower income, education, etc., do somewhat worse than Wallerstein's more advantaged subjects