Having multiple sexual partners is a significant predictor of
women turning to drink and drugs in later life, a new study
The study, based on a world-renowned programme that has
followed 1000 people born in Dunedin 40 years ago, is
believed to be the world's first to show the pattern.
Women who averaged more than 2.5 sexual partners a year in
the years leading up to each interview with the researchers
were 10 times as likely as women who had only one or no
sexual partners a year, to be clinically dependent on alcohol
or drugs at age 21. They were seven times as likely by age 26
and 17 times as likely by age 32, even after allowing for all
other factors in their lives.
The relationship was weaker for men.
A researcher in another long-running study in Christchurch,
Dr Joe Boden, said the Dunedin finding was ''novel'' because
everyone until now had thought the drink-sex link ran only
one way - from alcohol to sex.
''It's an argument about reciprocal causality, where it
creates a kind of feedback loop,'' he said.
One of the Dunedin authors, public health professor Charlotte
Paul, said the study pointed to mental health risks for women
in having many sexual partners, and the obvious physical
risks of sexually transmitted diseases.
''At present, we are engaged in some very proper discussion
about individuals committing to each other in marriage for
gay people, but we don't seem to be talking about this at all
in terms of heterosexual activity.''
The study found that men born in Dunedin in 1972-73 were
still more likely than women to have multiple sexual partners
between 18 and 31.
Similarly, 27% of men, but only 12% of women, were dependent
on alcohol or drugs at age 26, ''dependent'' meaning their
drug-taking or drinking seriously affected their work or
But for men, the number of sexual partners made little
difference to their chances of being drink or drug-dependent.
Women who had fewer than about 15 partners in their early 20s
were less likely than men to be substance-dependent. But
above about 15 partners they were more likely than men to be
substance-dependent, and that likelihood increased steeply
the more partners they had.
This pattern was found after adjusting for other factors,
including previous drug and alcohol problems.
The researchers said the link between the number of partners
and later substance dependence might be because of the
''shared context'' of drinking and meeting people in bars, or
to both behaviours being related to underlying risk-taking
But they said the much stronger effect for women suggested
that having multiple partners directly heightened the risks
of later substance dependence for them.
''Men and women may have different motives for having sex.
Women often say it is for love, commitment and emotional
reasons and while men also share these motivations, they may
be more likely to also participate in sex just for physical
reasons,'' they said.
''Self-'medication' with substances may be one way of dealing
with this interpersonal anxiety. But much more needs to be
known about why the association is so strong for women.''