If you want to read findings of various studies which examine, in part, co-habitation prior to marriage here's a good list (includes some of the studies themselves - straight from the journals - as well as books that cite the studies):
Deal with the social, economical, physical, and mental advantages to marriage as opposed to co-habitation:
S. Nock, Marriage in Men?s Lives (1998)
David Popenoe and Barbara D. Whitehead, The State of Our Unions: Social Health of Marriage in America (1999)
J. Gottman, The Seven Principles for Making Marriage Work (1999)
L. A. Lillard And L. J. White, ? ?Til Death Do Us Part: Marital Disruption and Mortality,? American Journal of Sociology, Mar. 1995
L. J. Waite, ?Does Marriage Matter?? Demography, Nov. 1995
W. R. Gove, ?Sex, Marital Status, and Mortality,? American Journal of Sociology, July 1973
J. S. Goodwin, W. C. Hunt, C. R. Key, and J. M. Samet, ?The Effect of Marital Status on Stage, Treatment, and Survival of Cancer Patients,? Journal of the American Medical Association, 4 Dec. 1987
J. A. Burr, P. L. McCall, and E. Powell-Griner, ?Catholic Religion and Suicide: The Mediating Effect of Divorce,? Social Science Quarterly, June 1994
L. N. Robins and D. A. Regier, Psychiatric Disorders in America: The Epidemiologic Catchment Area Study (1991)
?Sex, Marital Status, and Mortality?; S. Stack And J. R. Eshelman, ?Marital Status and Happiness: A 17-Nation Study,? Journal of Marriage and the Family, May 1998
Psychiatric Disorders in America: The Epidemiologic Catchment Area Study
R. H. Coombs, ?Marital Status and Personal Well-Being: A Literature Review,? Family Relations, Jan. 1991
W. R. Gove, C. B. Style, and M. Hughes, ?The Effect of Marriage on the Well-Being of Adults: A Theoretical Analysis,? Journal of Family Issues, Mar. 1990
W. Wood, N. Rhodes, and M. Whelan, ?Sex Differences in Positive Well-Being: A Consideration of Emotional Style and Marital Status,? Psychological Bulletin, 106, no. 2 (1989), 249-64.
R. R. Rindfuss and A. VandenHeuvel, ?Cohabitation: A Precursor to Marriage or an Alternative to Being Single?? Population and Development Review, Dec. 1990
R. T. Michael, J. H. Gagnon, E. O. Laumann, and G. Kolata, Sex in America: A Definitive Survey (1994)
G. T. Stanton, Why Marriage Matters: Reasons to Believe in Marriage in Postmodern Society; Marriage in Men?s Lives
Specifically deal with the researched ill-effects of co-habitation:
D. Blankenhorn, Fatherless America: Confronting Our Most Urgent Social Problem (1995), 330
F. Goldscheider, A. Thornton, and L. Young-DeMarco, ?A Portrait of the Nest-Leaving Process in Early Adulthood,? Demography, Nov. 1993, 695.
Council on Families in America, ?Marriage in America: A Report to the Nation,? in D. Popenoe, J. B. Elshtain, and D. Blankenhorn, eds., Promises to Keep: Decline and Renewal of Marriage in America (1996)