Mr Crombie and wife Norma, of Dunedin, have been married for 60 years, and he believes marriage offers couples a solidarity de facto relationships do not.
In a de facto relationship, "there would always be just that wee shadow of doubt", whereas a marriage was "signed and sealed", he said.
He agreed with a study released yesterday which found being married was positive for the mental health of both men and women.
On the other hand, ending a marriage, through separation, divorce or death, resulted in increased risk of mental health disorders, particularly substance abuse for women and depression for men.
The international study, led by clinical psychologist Dr Kate Scott, of the University of Otago, Wellington, involved about 35,000 people in 15 countries.
It was based on the World Health Organisation World Mental Health surveys and was recently published in the United Kingdom journal Psychological Medicine.
"What our study points to is that the marital relationship offers a lot of mental health benefits for both men and women, and that the distress and disruption associated with ending marriage can make people vulnerable to developing mental disorders," Dr Scott said.
She decided to become involved in the study because previous research on the subject had had "conflicting" results.
This study was more comprehensive than others and laid to rest "research urban myths", she said.
"What makes this investigation unique and more robust is the sample is so large and across so many countries, and the fact that we have data not only on depression, which has been much studied in the past, but also on anxiety and substance use disorders.
"In addition, we were able to look at what happens to mental health in marriage, both in comparison with never getting married, and with ending marriage."
While the study focused on single and married people, she believed the findings may extend to de facto couples.
The study did not offer any reasons behind the differing effects on mental health, but Dr Scott said "common sense" and other research showed humans needed the "companionship, intimacy, closeness, good health, sustenance and support" often found in marriage.
